Abarim Publications' online Biblical Greek Dictionary
The noun ετος (etos) means year (Matthew 9:20, Luke 3:1, John 2:20). This word comes from an ancient root, and also exists in Sanskrit (as vatsa) and Hittite (as whitish). And since longer periods of time are commonly expressed in years, the Latin word veteranus, from whence comes the English "veteran", makes use of the same root.
This word is used 49 times in the New Testament, see full concordance, and also occurs in the New Testament as part of the following compounds:
- Together with the adverb δις (dis), which comes from the familiar cardinal number δυο (duo), two, and which means twice: the adjective διετης (dietes), meaning of two years [old] (Matthew 2:16 only). From this word comes:
- Together with the cardinal number εκατον (hekaton), meaning a hundred: the adjective εκατονταετης (hekatontaetes), meaning centenarian or of a hundred years [old] (Romans 4:19 only).
- Together with the cardinal number τεσσαρακοντα (tessarakonta), meaning forty: the adjective τεσσαρακονταετης (tessarakontaetes), meaning of forty years (Acts 7:23 and 13:18 only).
- In plural and together with the cardinal number τρεις (treis), meaning three: the noun τριετια (trietia), meaning three years (Acts 20:31 only).
The curious noun ενιαυτος (eniautos) also means year, or more precise: anniversary (a word that comes from the Latin word for year, namely annus, plus the verb verto, to turn or return). Our noun combines the common preposition εν (en), meaning in, at, on, with the familiar pronoun αυτος (autos), meaning self.
In the classics this noun is often used as synonym of ετος (etos), meaning year (see above), but because it doesn't actually speak of any particular length of time, merely the fact that we've gone full circle, it also became used to signify a return or completion of much greater cycles (up to 600 years). It is used 14 times in the New Testament; see full concordance.