Autological word

An autological word (or homological word) is one that expresses a property that it also possesses. For example the word "pentasyllabic" has five syllables, and the word "writable" is writable.

The opposite is a heterological word, one that does not apply to itself. For example the word "long" is not long, "monosyllabic" has more than one syllable and "non-hyphenated" is hyphenated.

Unlike more general concepts of autology and self-reference, this particular distinction and opposition of autological and heterological words is uncommon in linguistics for describing linguistic phenomena or classes of words, but is current in logic and philosophy where it was introduced by Kurt Grelling and Leonard Nelson for describing a semantic paradox, later known as Grelling's paradox or the Grelling–Nelson paradox.

One can ask: Is "heterological" a heterological word? If the answer is "no", then "heterological" is autological. This leads to a contradiction, for in this case "heterological" does not describe itself: it must be a heterological word. But if the answer is "yes", then "heterological" is heterological. This again leads to a contradiction, because if the word "heterological" describes itself, it is autological.