Feminine forms of adjectives in -ων: why ἀέκουσα, but not ἀπείρουσα, ἀμύμουσα?

Question

The wiktionary entry for -ων says it's an ending cognate with stuff like Latin -ens, -iens, and gives the feminine as -ουσα. Therefore it makes sense that we get ἀέκων, ἀέκουσα. But then we have ἀπείρων and ἀμύμων, which are the same in their masculine and feminine forms (at least as shown in wiktionary's declension tables).

Is there some way to tell which words are going to decline which way? Or is it instead the case that all of these words decline the same way, but their wiktionary articles are documenting different time periods or dialects?

Answer 1

ἀέκων is morphologically a participle (or rather a negation of a participle ἕκων "willing"); it declines just like present participles of the λύων type, so its stem is ἀέκοντ-, and the feminine is ἀέκουσα like λύουσα. You can tell this from its dictionary entry, which should tell you that the genitive masculine is ἀέκοντος (rather than ἀέκονος).

Most other nouns and adjectives in -ων didn't originate as participles, so they don't have the τ. Usually they have a stem in -ον-, but sometimes (especially with names and words for people) they keep the long vowel in the stem, -ων-. Again, the dictionary entry should tell you what the stem is.

When you see a noun or adjective in -ων it's usually safe to assume it falls into the second class. A common exception is ἄρχων, ἄρχοντος "ruler", which again is originally a participle ("the one ruling").