“Autology” is a word that was fairly rare even when it was in use back in the 1600s. It meant self-knowledge, or the study of oneself. Some years later there was also the form “autological” for referring to things having to do with autology. Since Freud didn’t happen across the word, it probably would have disappeared completely except for a new meaning that arose in the 20th century: words that are instances of themselves began to be called “autological” in a 1926 academic paper.
What it means to be a word that’s an instance of itself is a word like “word” — it is, itself, a word, so it’s an instance of itself. So is “noun.” “Noun phrase” is a noun phrase, so that’s another one. There are a few others: “unhyphenated” is not hyphenated, which makes it autological. “Short” is a word that’s pretty short. The word “prefixed” is prefixed (with “pre.”) And an obscure one is “adjectival;” since it’s an adjective, it’s also autological.
Words that aren’t autological — which obviously is almost all of them — are “heterological,” at least according to the 1926 paper, which was by F. P. Ramsey. It was published in, of all places, the “Proceedings of the London Mathematical Society.” This was very helpfully pointed out by Bertrand Russell in 1940, when he wrote “‘Long’ is heterological because it is not a long word.”
There seem to be many more autological adjectives than there are nouns. “Terse,” “erudite,” readable,” “sesquipedalian” (it means “a long word”), “polysyllabic,” “descriptive,” and “common” are, well, fairly common ones. So is “useful”, which is how you don’t describe the websites like this one. The sites are helpful though, if you find yourself writing a short explanation about “autological words.” In that one situation they save you from having to think up all your own examples. There are some edgy examples too, of course — “edgy” because you could dispute them. For example, “missppelled” MIGHT be autological because it’s misspelled. But when it’s misspelled, particularly on purpose, does it still qualify as a legitimate word? More acceptable, depending on the variety of colors of inks you have available, would be “green” (written in green ink), “purple” (in purple ink), and so on. And here’s another autological noun phrase, although this one depends entirely on its context: “the end.”
