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13-letter words ending in X

Eight 13-letter words ending in X make this a short, rare list, with four entries tied for the top score of 30 points.

8 wordsTop pick ARCHAEOPTERYXHighest score ARCHAEOPTERYX 30

S ends the most 13-letter words (7,018); K ends the fewest (7). X ranks #17 of 26. The bar under each letter shows the size of its list.

Best words to play first 8 · most-used first

  • ARCHAEOPTERYX30
  • CEPHALOTHORAX30
  • ULTRAORTHODOX24
  • HIERACOSPHINX30
  • IMMUNOCOMPLEX30
  • IMPROVISATRIX27
  • INTERLOCUTRIX22
  • PRIMOGENITRIX25
All valid words 8

A to Z. Includes rare and Collins-only words. Linked tiles open the word's meaning, score and rhymes.

  • ARCHAEOPTERYX30
  • CEPHALOTHORAX30
  • HIERACOSPHINX30
  • IMMUNOCOMPLEX30
  • IMPROVISATRIX27
  • INTERLOCUTRIX22
  • PRIMOGENITRIX25
  • ULTRAORTHODOX24

Highest-scoring words

Scrabble and Words With Friends points, before board bonuses
WordScrabbleWords With FriendsDictionaries
ARCHAEOPTERYX3030All three
CEPHALOTHORAX3031All three
HIERACOSPHINX3031Collins only
IMMUNOCOMPLEX3038Collins only
IMPROVISATRIX2730Collins only
PRIMOGENITRIX2529Collins only
ULTRAORTHODOX2425All three
INTERLOCUTRIX2226Collins only

None of these eight words is classified as common, and Collins accepts all eight while ENABLE and NWL2023 each include three. Four tie at 30 points, so the rare X ending offers more scoring potential than everyday recall. The examples range from archaeopteryx to interlocutrix, with three beginning in I and five starting with other letters.

How many 13-letter words ending in X are there?

  • Exactly 8 tournament-dictionary entries have 13 letters and end in X.
  • Collins includes all 8, but ENABLE and NWL2023 each include 3.
  • Three entries start with I: immunocomplex, improvisatrix, and interlocutrix.
  • Four words score 30 points: archaeopteryx, cephalothorax, hieracosphinx, and immunocomplex.
  • The 13-letter S-ending list has 7,018 entries, far more than this X-ending set.

Which X-ending entries score highest?

Archaeopteryx, cephalothorax, hieracosphinx, and immunocomplex each score 30 points. Their shared top score makes them the first names to check when a long rack or board opening gives you room for a 13-letter play.

The next scores step down quickly: improvisatrix scores 27, primogenitrix 25, ultraorthodox 24, and interlocutrix 22. That spread puts the lowest scorer 8 points behind the four leaders, before any board-square bonuses.

These spellings are not equally familiar. Archaeopteryx and cephalothorax are more recognizable examples, while hieracosphinx and interlocutrix are specialized vocabulary. Knowing the exact spelling matters: each word must use all 13 letters and finish with X.

When to play 13-letter words ending in X

Treat the set as a pattern-solving aid, not a list to memorize wholesale: none of its entries is common, and dictionary coverage differs. Collins has all eight, whereas ENABLE and NWL2023 each have three, so check your game's word list before committing to an unfamiliar term.

For a quick search, start with the three I-words or the four entries tied at 30 points. The comparison with 13-letter words ending in Y is striking: that neighboring pattern has 1,563 entries, against just 8 ending in X.

Questions people ask

Are 13-letter words ending in X common?
No, none of the eight entries is classified as common. The set includes specialized words such as hieracosphinx and interlocutrix alongside more recognizable archaeopteryx and cephalothorax. That rarity makes spelling and dictionary coverage worth checking before you play an unfamiliar entry.
Which starting letter appears most in this list?
I is the most frequent starting letter, with three entries: immunocomplex, improvisatrix, and interlocutrix. The other five words each begin with a different letter: A, C, H, P, or U. That gives you a useful clue when narrowing a rack pattern.
Do all game dictionaries accept these X-ending words?
No, coverage varies by dictionary. Collins includes all eight entries, while ENABLE and NWL2023 each include three. The counts do not identify which specific words overlap, so verify an unfamiliar choice in the word list used by your game.

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