C.1. General Remarks on the Concordances

1. The concordances aim to show the relationships among the three main Maya glyph-classification systems in use today: (i) the MHD codes, used in the Maya Hieroglyphic Database to encode a substantial portion of known Maya inscriptions; (ii) Bonn's TWKM codes, the recent rework and extension of the Thompson numbers by the Bonn University TWKM Project; and (iii) the well-established, but outdated, Thompson numbers, often encountered in published papers. Corresponding CMGG entries are also given when they exist; these provide many further glyph-variant examples and extensive diagnostic, linguistic, and other information.
2. The are several concordances available on the page, which you can choose with the "Primary" radio buttons. The Thompson concordances are yet to come, so that choice is currently inactive. However, the following documentation may refer to their expected functionality.
3. In general, the set of codes (or logogram and syllabogram names in the case of CMGG) for the chosen primary catalog / listing will be in the first column of a displayed table. The other columns of a table will show the codes from the other system(s) corresponding to the first-column code / name. In the case of MHD and TWKM subsorts / subcodes, the corresponding Thompson number is also indicated below each subcode (TWKM) or subsort (MHD). In all except the Thompson Concordance, the graphics for these Thompson numbers are given in the Thompson (third) column. Finally, in all except the CMGG Concordance, the last column will have links to CMGG entries corresponding to the meanings / translations given for the MHD and TWKM codes in the row.
4. The concordances available are:
   • TWKM Concordance. The first column contains all TWKM codes, grouped by sign number. The TWKM sign numbers (in bold) are padded with leading zeroes to help with searching by Ctrl-F on the page. For each TWKM sign number, the corresponding MHD code(s) for the TWKM codes with that number are given in the second column. The specific MHD code corresponding to a given TWKM code is indicated below the TWKM code, or it may indicate that no corresponding MHD code has been found. The TWKM codes include "full-figure" graphs (code suffix starts with "f"), which are typically one-off creations and usually not included in the MHD Catalog: these are notated as "unique". In some cases there will be other specific notes regarding the MHD view on a TWKM code. This may be under the graphic or in the MHD column.
   • MHD Concordance. The first column contains all MHD codes. For each MHD code, the TWKM sign number(s) for which at least one code corresponds to at least one MHD subsort are given in the second column. As with the TWKM-MHD Concordance, the Thompson and LMGG columns contain the Thompson numbers and CMGG words/syllables corresponding to the TWKM and MHD codes in the row.
   • CMGG Concordance. The first column lists all CMGG logogram and syllabogram names. The MHD column contains all MHD codes for which at least one of the readings coincides with the CMGG entry name. Similarly, the TWKM column contains all TWKM signs with at least one of its readings corresponding to the CMGG entry name. Sometimes additional codes/signs may occur in the MHD and/or TWKM columns, especially some with no pronunciation / translation. These are being picked up because of having been matched to to a code in the other (MHD or TWKM) system which has the CMGG reading: there are some differences between MHD and TWKM as to which readings apply (or not) to certain glyphs.
5. The drawings given by Thompson and TWKM for their signs, while based on real-world occurrences, have been somewhat idealized, both to smooth out and regularize lines and to capture what they regard as essential features of the glyph. The MHD drawings represent, by contrast, actual instances of glyphs on a specific real-world monument, piece of pottery, or other artifact. These drawings are from the MHD Catalog, used by kind permission of the artist, Matthew Looper. By using the MHD code given under an MHD example, drawings of a very large number of instances of the glyph across thousands of inscriptions on real-world objects can be found in the main part of MHD.
6. The spellings given for the TWKM, MHD, and CMGG entries are those provided by their respective authors and so the same conceptual "word" may appear in slightly different forms in the table entries. See B.2 and D.5(c) below for more on this.
7. Thompson did not provide readings or translations for most of the glyphs he identified (indeed the major progress in Maya decipherment did not take place until after publication of his work).

1. MHD Codes and Glyphs. These are from the MHD Catalog, released in early 2022, with subsequent significant additions. The completely new Looper-Macri sign classification system (MHD codes) formed the foundation for the massive undertaking (substantially achieved, but still being enlarged) to make a database of all known Classic Maya and Maya codex inscriptions. This is the Maya Hieroglyphic Database (MHD), which can be searched for free. To search effectively, one needs to use the MHD code(s) for the glyph(s) of interest. Therefore, if you have found a glyph of interest using TWKM code, T-number or word search, finding the MHD code given on the same row can provide a large number of additional real-world examples and other information. See here for further information on searching MHD.
2. TWKM (Bonn) Codes and Glyphs. These are from Bonn University's Dictionary of Classic Mayan project, partially released in late 2022, with subsequent additions, including a very substantial one in August 2025 that for the first time included meanings / translations for their codes. The TWKM system is a rework and extension of the Thompson numbers (see below) that incorporates the signs found, and the enormous progress made in Maya decipherment, since Thompson's 1962 book.

   TWKM codes are matched to Thompson numbers according to the concordance given in the TWKM Catalog/Dictionary (link above). Note that TWKM only provides a full Thompson number in its concordance, while a given TWKM code may only graphically correspond to one or more parts of a Thompson number that has parts (suffixes a,b,c...). The intended part(s) are usually clear from a visual examination (in some cases Thompson grouped signs under the same number even though it is now known that they represent different glyphs).

3. Thompson numbers. Some of the images for the Thompson glyphs are quite small, so a zoom facility has been provided to enable examination of their details when wanted. Click once on an image to magnify it and click again to revert. You can of course also right-click on the image and open it in a new tab, where you can magnify it as much as you want with Ctrl-scroll and also drag the tab out of that window to create a new one alongside for comparisons.

   Thompson's original 1962 publication is available online (need to log in and borrow). It includes, for most glyphs, the lists Thompson collected of where the glyphs were known to occur. Some points regarding the Thompson glyphs:

   1. The glyphs for Thompson (and TWKM) numbers 1-370 are "affixes". For Thompson glyphs, each drawing typically contains several versions of an affix. These are placed around a square that represents a "main" glyph (those from 500 onwards, called "main signs" by Thompson) to which the affix would be attached (the square itself is not part of the affix). The part indicators a, b, ... typically refer to the glyph variations starting on the left of the square (9 o'clock position) and proceeding clockwise around it. In this case, the intention is that each version of the affix is "fully rotatable", that is, it can appear in any position, not just the illustrated one.
   2. In some cases, the different versions of an affix are not given in the usual clockwise placement. This indicates that Thompson believed, based on the examples he had collected, that the affix only occurred in a certain position(s) relative to the sign to which it was attached. This would typically be vertical (left or right) only or horizontal (top or bottom) only, but sometimes as specific as only on the left (prefix), only on the top (superfix), only on the right (suffix), or only on the bottom (subfix). For example, T97ab shows two versions of an affix that are only expected be seen vertically and T98ab gives two that are only expected horizontally.
   3. Sometimes affixes are shown, for economy, with just a vestige of the square, to still indicate typical placement of the affix (again, the vestigial square part is not part of the affix). For example, the T100c sign is being shown as expected only as a prefix (otherwise it would have been combined with the T100ab drawing). Similarly, T241 is indicated as being only a subfix.
   4. This all having been said, and while some of the restricted placements make sense in terms of what the affix represents, Thompson was operating off a smaller set of data than is available today. Also, the carvers and writers of Maya inscriptions were often very creative. Therefore, one may occasionally find the affixes in positions other than those given by Thompson.
   5. More generally, while the glyphs for affixes and main signs are the building blocks of Maya writing, the basic unit in most inscriptions is the "glyph block". This is a combination of several glyphs within a square or rectangle, and again the individual glyphs may be creatively represented and positioned, including placement of one glyph inside another (infixing), merging of two glyphs (conflation), partial obscurement by other glyphs, relative size change of constituent glyph parts, etc. There have also been cases discovered where glyphs identified by Thompson as affixes have independent occurrences (i.e., are "main signs").
4. CMGG Entries.
   1. The CMGG entries given on a row are based primarily on the TWKM and/or MHD readings for their glyphs that appear on the row (see C.2(c) below for how these are chosen). Generally, a CMGG entry is given corresponding to each reading given by TWKM and MHD, even when these may not agree. This is to help the user assess the given readings.
   2. The spelling used for a CMGG entry link may differ from that given by TWKM or MHD (which may themselves differ from each other and from other authors). This is because the exact pronunciation of Classic Maya words (as used over a thousand years ago) is not always known and even when agreed on, different epigraphers use different spelling conventions. Typical variations include presence, loss, or substitution of "H", "J" and the glottal stop, and the use of doubled letters to indicate long vowels.

   3. In some cases, a CMGG entry is given on a row in addition to those corresponding to the TWKM and/or MHD readings, or even when no TWKM or MHD reading exists. These are cases where we feel that the given CMGG entry is nevertheless relevant to the glyph(s) on the row. Conversely, some rows have readings given in TWKM and/or MHD but no CMGG entry. This is because the CMGG author is not familiar with that particular glyph, because it has not occurred in inscriptions that he has studied thus far. Updates will be made in future releases, corresponding to future editions of the CMGG.

The table below summarizes possible ways to search for glyphs. More detail on some aspects is given following the table.

1. Basic search. The most basic search for anything on the front or other site page is, as with any website, by using Ctrl-F. Some browsers, such as Firefox, natively support case-sensitive and whole-word searching, which is useful for finding logogram names (traditionally written in all-caps), including CMGG logogram entries (see D.5(c) below for more search tips on these), and for MHD codes. Other browsers, such as Chrome, only support such searching via add-ons (see Regex search below).
2. Thompson numbers. Thompson numbers often appear in books and articles in a form like T638. To search the Home Page grids for this, just search (Ctrl-F) for T638. This will often find the T-number, but it does not for T638. This is because not every Thompson glyph has a corresponding CMGG entry (for example, some are still undeciphered and CMGG does not contain many undeciphered glyphs). For this reason, when searching for a Thompson number, it may be more efficient to use the Concordances which have more of the Thompson glyphs (see row S1 of the table above).
3. MHD codes. Searching the Home Page for MHD codes is easy: just search for the three-letter code. This will often be a unique string on the page, but sometimes may be part of some other text: using case-sensitive or whole-word search (native in Firefox and available by add-on for Chrome, etc. (see D.6 below)) can help with this. As with Thompson numbers (see above), not all MHD codes occur on the Home Page, so you may want to search the Concordances instead.
4. Syllabograms. These are given in the Syllabograms grid on the Home Page. The grid displays only one example for each syllabogram, but the linked CMGG entries give many variants. Additional variants may sometimes be found in the CMGG Concordance, where syllabograms are listed at the end of the table.
5. Logograms. As noted elsewhere, and as can be seen from the table entries, the spelling (transliteration) of a Maya logogram can vary depending on the author of the work where it occurs. Spelling conventions have also changed over time, as has the very "reading" of some logograms and their accepted meaning(s). Because progress in Maya decipherment has been so rapid over the last decades, if you're searching for something using spelling in a source from more than a few years ago, be prepared to find something totally unrelated to what was under discussion. Fortunately, for this very reason (and because of an initial lack of decipherments), many academic works provide Thompson numbers (T-numbers) for symbols mentioned, and these have never changed. Similarly, if an academic work mentions the MHD or TWKM (Bonn) code for a symbol, then that can be used for searching. See D.2 and D.3 above for searching for Thompson numbers and MHD codes. For more on searching for a logogram name / word based only its spelling, see (c) below. Some additional tips:
   1. Having found a Home Page grid cell or Concordance row by T-number, MHD or TWKM code, or an actual spelling of a Maya word, do not be alarmed if the glyph shown in the source does not seem to match what is there. If the source is discussing a real-world occurrence of a glyph, then the shape may differ greatly from the canonical version or example (see C.2(b)(v) above). CMGG entries will usually provide additional variants for it, some of which may be closer to the source occurrence.
   2. In the CMGG Concordance, you can find the row for a given word / CMGG entry just using Ctrl-F,
   3. When searching for a logogram name / word "from scratch", it is usually best to start with a case-sensitive search with the word in all-caps (that is how logogram names are represented on the site). If a first search does not yield a result, or is obviously not the desired one, you can try to:
      • change to a case-insensitive search, in case the word has only a syllabogram spelling or is part of a phrase (these are given in the Home Page grids in lowercase italics);
      • change short vowels (single vowel letters) to long (double the vowel letter), or vice versa;
      • substitute H, J or ' with one of the other two, or delete them (but not following a vowel at the end of a word, because logogram names hardly ever end in a vowel);
      • change CH to K or vice versa;
      • change a vowel followed by H to a doubled vowel and remove the H (but not at the end of a word), or vice versa.

      If you know the meaning / translation of the word or its abbreviated nickname (e.g. QB for the quadripartite badge), then you can search for that, although the translations given in the Home Page grid cells or Concordance may use different English words than you have thought of. In any case, use a case-insensitive search.

      If searching the Home Page or Concordances is not yielding results, you can try searching the full CMGG PDFs: see D.7 just below.

6. Regex search. If you use Chrome or another browser that does not immediately support case-sensitive and whole-word searching, it is highly recommended to get an add-on with a "regular expression" (regex / RE) search facility. This allows not only case-sensitive and whole-word search (use the regular expression ^ABC$ to find ABC only as a whole word, not embedded in another string), but also searching with wildcards and so forth.
7. CMGG search. Searching across all of CMGG to find, for example, any entries in which a certain piece of text, name, alternative spelling or old reading occurs can only be achieved currently by searching the PDF version of CMGG.
8. Glyphs with a certain visual appearance. If you have in mind a certain glyph but cannot recall its reading (or maybe it doesn't have one), but you recall some of its shape / characteristics, all may not be lost. Some approaches:
   1. Searching the TWKM glyphs. The TWKM Sign Catalog has several filters which may be useful in reducing the number of glyphs to scan. In particular, under the Graph filters (left menu), the Iconography sub-filter allows selection from an extensive list of visual features. In general this is probably the fastest way to locate a glyph with particular features/properties, once you get used to the system. As an example, for glyphs involving snakes, start by clicking the "Expert" icon to the right of the "Or" button under Iconography. This brings up a menu with a Search box at the top and a choice of two submenus, "graph composition" and "iconography". You can look through the terms in these menus and their sub-(sub-...)menus to get an idea of the terms available. For snakes, even though there is no term of exactly "snake", we're lucky and typing "snake" into the Search box brings up "rattlesnake" under agent > animal taxon > reptile > serpent. Selecting the checkbox for "rattlesnake" and using the Save button at the far bottom right of the popup brings up only one glyph. However, if instead you select the more general "serpent" category (and again Save), then you will get just over 20 results which may well contain the glyph you had in mind.
   2. Using the MHD classification system. To the extent that the characteristics you recall fit the MHD classification system, you can look for the glyph among those with MHD codes starting with the relevant two-letter category indicator. For example, if you recall that the glyph you're looking for contains a snake, you can look at the glyphs with MHD codes starting with "AC" (A = animals, C = snake in the the MHD classification system). To do this, you can go to the MHD Concordance (Concordances page and select MHD as the primary column). The MHD codes in the first column are arranged in alphabetical order, so you can scroll down to, or search for, where the AC codes start and scroll through the AC codes to see if you can locate your glyph. Alternatively, you can scan visually through the AC section of the MHD Glyph Catalog. These are arranged alphabetically by code, so it is easy to search the PDF (use Ctrl-F) to find the first occurrence of, for example, "AC".

      Keep in mind, however, that, for example, something you regard as "snake-like" may be classified not as AC* but under something else, often in the groups starting with X or Z. Indeed, there is a very distinctive glyph XF6 containing a snake. This is an unusual case and the MHD categories are generally very helpful, but do just keep in mind that a glyph may in fact still be around even if you don't find it in the category you thought to use for searching.

   3. Scanning the Thompson glyphs. Again this can be done by scrolling down the Thompson Concordance, but it may be faster and easier on your wrist to visually scan the Thompson glyph catalog.

1. Inscription. Inscriptions are generally known by the object on which they occur, given in this column by its modern-day name, followed by any older names and the abbreviation used in MHD for the object (MHD's "objabbr" field), useful in conducting searches there.
2. Photos and 3D Models. Gives publicly available photos of the object on which the inscription occurs and any 3D model that is available. The photos have generally been chosen to include as much of the inscription as possible as well as to give an idea of the nature of the object and its (current and/or former) environment, when possible. Older photos may show detail in an inscription that is no longer visible today due to erosion, fading and/or damage. 3D models tend to be made from the oldest available version of an object, which can be moulds made by expeditions that occurred as far back as the 1800's.

   To see all the photos at once, use the "All-in-One" link, which will show them in a scrollable list in a window on the left side of the screen, giving the URL for each photo just above it. If the URL begins with "mhd2", it means the image is in the Maya Hieroglyphic Database.

   Left-clicking on a thumbnail will bring up a photo in a separate window. Each one, whether from the same or a different inscription, will by default replace the previous one. To bring up multiple photos at once, use the right mouse button to bring up the standard browser menu and open each in a new tab or window.

   3D model manipulation. Clicking on a 3D Model box will bring up the model in its own browser window. 3D models are typically hosted on Sketchfab. To manipulate the 3D models, experiment with using your mouse buttons and scroll, often together with Shift, Ctrl, Alt and Win/Cmd keys. In general, move the mouse fairly slowly and there may be some lag in getting the response from the model.

   For Sketchfab models, common manipulations can be achieved as follows:
       Rotate: Drag left mouse button
       Move: Shift + drag left mouse button
       Zoom: Turn wheel on a scroll mouse; Ctrl + drag left mouse button
       Change incident light angle: Alt + drag left mouse button (slowly)

3. Summary. A summary of the content of the inscription as well as any distinguishing features.
4. Inscription Dates. The creation date of the inscription, according to MHD's "objlc" (object long count) field, defined as the "creation date of [the] text in long count notation". The column has the Long Count (LC) and the corresponding Julian date in YYYY-MM-DD format. This is followed by the dates of events recounted in the inscription, given in the same formats.

1. HTML panes. The HTML page consists of three panes:
   • Left pane: The drawing(s), with coordinates
   • Middle pane: The TTT Table
   • Right pane: The Introductory Notes and End Notes
2. HTML Relative Positioning. These panes can be scrolled independently to enable the drawing of a glyph-block to be physically close to the TTT of that glyph-block and to any end note relating to that glyph-block. Clicking on end note numbers in either the middle or the right pane will cause the the other pane to be repositioned so as to have the TTT table row or end note with that number at its top.
3. HTML Zooming. Zooming in or out of each of the panes (using a scroll-mouse or Ctrl+/Ctrl-) can also be done independently. This feature is particularly useful when the user wishes to zoom in on the drawing of the glyph-blocks in the left pane. This can be done without a corresponding zooming in of the middle and right panes. This means that the letter size which is comfortable for reading by the user remains at that size when zooming in or out of the drawing in the left pane.
4. TTT Table columns. The TTT table (middle pane) has the columns below (from left to right). For additional detail on these, please see section D of Background to the TTTs.
   • Coordinates (glyph-block labels): These are given in the usual A1, B1, A2, B2,... system with letters for the columns and numbers for the rows. Usually there’s one table row per glyph-block but complex blocks may be broken down into two ("a" = left side and "b" = right side) or four (a, b = left top and bottom, and c, d = right top and bottom. Sometimes there may be more than one coordinate system given: if so, this will be explained in the Introductory Notes.
   • MHD Codes (user-selectable in HTML; not present in PDF): The codes given in MHD ("blcodes") for each glyph-block or part thereof. Note that MHD sometimes divides (or does not divide) blocks into parts differently than the coordinate system used for the TTT, but the correspondence is usually obvious. The MHD codes link to the set of drawings that MHD gives as comprising that code. Note that MHD updates its readings, codes and constituent graphemes from time to time and there could be periods when the MHD codes given do not yet completely agree with the MHD live site, which should always be consulted in case of doubt.
   • Transliteration: Given as Maya words (logogram names) and syllables (syllabogram names), with "joiner notation" (see Useful Popups above). Links are given to the corresponding CMGG entries. The transliteration occasionally varies from that given in MHD: in this case a linked End Note will explain why.
   • Translation: The translations are intended to strike a balance between literal and idiomatic and will often vary in their exact wording from those given in MHD; if the meaning is substantively different, a linked end note will discuss why.