14 Therefore the Lord himself shall give you a sign; Behold, a virgin shall conceive, and bear a son, and shall call his name Immanuel.
Many a secular & Jewish scholar today want to say that this verse actually reads, "The Lord himself shall give you a sign; Behold, a young woman shall conceive & bear a son..." Well, firstly, that is NOT how it was understood for the hundreds of years prior to the rise of Christianity. The LXX, written some 300 years before Christ, clearly uses the word virgin. This was the classical Jewish interpretation for at least 1000 years after Christ.
Then, in the 10th c. AD, in reaction against the dominance of Christian culture in Europe, the Masoretes began saying that, "No, it only means young girl, not virgin," & atheists & secularist have latched onto that interpretation ever since, as it fits comfortably in with their view of scripture. This is because if this reads "young girl" then Matthew got it wrong when he used it as prophetic support for Mary's virgin birth. That would mean there are errors in the NT, which means there is no inspired text; the Bible is just a book of man, not the Word of God.
However, the facts do not support such a position. Firstly, the point made above -- the "young girl" interpretation was made in reaction to its use by Christians. That makes the veracity of the interpretation suspect. Secondly, simply read the context. God is to send a sign. The revisionists would have us believe that the great sign from God will be that an unnamed woman will have a child in the normal, everyday fashion. This hardly sounds like a sign! What do you think? Is a girl getting pregnant so extraordinary an event that you would say, "Oh! Look! A sign from God! A woman is pregnant!" That hardly seems tenable. You're left with asking, "Where's the sign? His name?" That hardly seems significant. She's going to give him a name. Oh! Wow! Must be from God! No one would ever name their kid "Emmanuel" after seeing it in Isaiah ... noooo! That's not a sign from God. Any woman could give their kid this name! A sign from God has to be seen as coming only by Him, made possible only by Him. Getting pregnant & giving a kid a name would hardly stand up to that test!
Now, a virgin having a child -- that's extraordinary. It would also set this anonymous woman apart from all other pregnant women. A perfect creation in the womb of woman, ex nihilo by only the Word of God . . . now, THAT's a sign! Of the two interpretations, only the classic "virgin" interpretation is supported by the context & the intention of the text.
Remember, there is no dispute that this word can & often does mean "maiden" or "virgin." It can also mean "young woman." What determines its use is context. The context here is that of a miracle, a sign from God, &, sorry, a girl getting pregnant simply does not qualify as a valid interpretation in the context. "Virgin" does.
So, Matthew uses the mainstream interpretation of his time; an interpretation that was classical, going back at least hundreds, if not thousands of years; an interpretation that is readily found in all rabbinical literature prior to the rejection of the Messiah by the Jewish rabbinical elite. Only THEN did it have to mean something else, anything else other than they were wrong in crucifying their own Messiah. The case is laid bare. You decide.