Abarim Publications' online Biblical Greek Dictionary
The noun παρθενος (parthenos) means virgin and has nothing to do with a lack of sexual experience or physical intercourse. Our English word "virgin" comes from the Latin word virgo which either derives from or shares its root with virgo, which describes a fresh branch of a plant or tee. A virgo was a girl who still lived with her parents instead of with her husband. Since in antiquity sexual intercourse commonly resulted in pregnancy, and thus the decade and a half costly care for a child, no parent would allow their daughter to be impregnated by someone who didn't sign up for the duration. This was an economic consideration, not a sexual or moral one.
Our noun παρθενος (parthenos) is used 14 times in the New Testament, see full concordance, but most famously in Matthew 1:23: "...the parthenos shall be with child," which quotes Isaiah 7:14. Not directly obvious in Greek, the latter doesn't use the common Hebrew word for young woman, namely בתולה (betula), but rather the less common עלמה ('alma), which relates to the verb עלם ('alam), to be hidden or concealed, and the noun עולם (olam), forever or everlasting.
In the Christian era, Matthew's quote of Isaiah's famous statement allowed for the revival of the mother-goddess cult, but neither Joseph nor anybody in the original audience of the gospel would have missed the obvious reference to Pallas Athena, whose famous epithet was Parthenos.
In recent antiquity, "the Virgin" was Athens, and both Isaiah and Matthew spoke of statecraft rather than an embarrassing pregnancy of a supposedly innocent girl. Joseph's consternation upon hearing the angel's words rather stemmed from the mystery of how the great Athenean experiment of democracy (a popular rule without a king), which had so sadly failed, was somehow applicable to his young fiancée. Likewise the parable of the ten virgins is not about ten young girls but about ten democracies (Matthew 25:1).
- The noun παρθενια (parthenia), meaning virginity, again not denoting sexual innocence but rather the period of a girl's life spent with her parents. This word occurs in Luke 2:36 only, applied to Anna the prophetess, which is again a reference to Athens, or rather the council of wise men whose governance of the people had quickly failed but whose legacy had always remained faithful to the greater universal Truths.