εἴσεται

From LSJ

Ὅτι οὐδὲν ἧττον τὰ αὐτὰ ποιήσουσι, κἂν σὺ διαρραγῇς → You may break your heart, but men will still go on as before

Source

French (Bailly abrégé)

3ᵉ sg. f. Moy. de εἶμι.