Quibus enim nihil est in ipsis opis ad bene beateque vivendum → Every age is burdensome to those who have no means of living well and happily
Cicero, de SenectuteGreek (Liddell-Scott)
εἶσι: εἶσιν, γ΄ ἐν. τοῦ εἶμι (πορεύομαι).
French (Bailly abrégé)
3ᵉ sg. prés. de εἶμι.