Word for having the perfect word for an occasion

I remember reading or hearing once that there was a word, I think of Greek etymological roots, that meant "having exactly the right word for an occasion."

It's rather frustrating that I can't remember this particular word, so I'm hoping someone else out there knows it!

apropos as defined here

very appropriate to a particular situation.

"the word 'conglomerate' was decidedly apropos"

From Online Etymology Dictionary

1660s, "opportunely," from French à propos "to the purpose," from propos "thing said in conversation, talk; purpose, plan," from Latin propositium "purpose," past participle of proponere "to set forth, propose" (see propound). Meaning "as regards" is 1761, from French. As an adjective, "to the point or purpose," from 1690s

Not Greek, but apropos nonetheless.

le mot juste, meaning "the right word", is a nice loan phrase from French which has slipped into English via the French Novelist Flaubert. It means the perfect word for a situation.

Plural would be les mots justes.

It even made its way into Urban Dictionary, here: http://www.urbandictionary.com/define.php?term=le+mot+juste