"A century is not a year."
Translation:Un secol nu este un an.
They're synonyms, so both should be accepted. "Secol" should be the default, though; "veac" is more archaic/poetic.
I was really surprised to see this word. I know it from my native language, Serbian. Although in it, it's "vek".
Same as Russian век for century. And funnily enough not at all related to vechi (old) but rather to an assumed Indoeuropean word for "overcome", which turned into Latin vincere (win, but English win has different roots) https://en.wiktionary.org/wiki/Reconstruction:Proto-Slavic/v%C4%9Bk%D1%8A