On the list of the 365 supposed prophecies Jesus fulfilled this is a main claim.
Missionaries will argue for days on end that the Hebrew הָעַלְמָה ha-al'mah (the young woman) in Y'shayahu / Isaiah 7:14 means virgin (and not "young woman").
In reality the Hebrew word in Y'shayahu / Isaiah 7:14 does not mean "virgin" it means "young woman." The Hebrew word for "virgin" is בתולה / b'tulah. The Hebrew for "young woman" is עַלְמָה / al'mah (the הָ / ha prefix means "the").
Young women may or may not be virgins, and a virgin may or may not be young!
The two Hebrew words are not interchangeable. -- but even if Y'shayahu / Isaiah 7:14 had said "virgin" the choice of word is NOT prophetic of a virgin birth of the messiah.
The status of the woman (virgin or not a virgin) is actually totally unimportant in the context of Y'shayahu / Isaiah 7:14.
It would not matter if the word in Y'shayahu / Isaiah 7:14 were בתולה / b'tulah -- virgin.
Not one bit.
Ergo the missionaries (including the anonymous author of Luke and Matthew) are making much ado about nothing.
You see, 2000 years ago most pagan gods were virgin births. Even Augustus Caesar (the first caesar) claimed to the product of a non-human (miraculous / godly) birth. Per the Romans a snake impregnated his sleeping mother and Augustus was born 10 months later. Per the Romans this "snake" was really the god Apollo, and Augustus Caesar was the son of Apollo.
Various pagan gods had "virgin" mothers. Hephaestus (a Greek god) was born to a goddess without her having sex (Appolodorus, The Library 1.3.5, 2d century BCE and Hesiod, Theogony, 929, 8th century BCE).
Early Christians admitted that the idea of a god born of a virgin or simply impregnated by a god without sex birth was not unique to Jesus. "we are not the only persons who have recourse to miraculous narratives of this kind. For some have thought fit, not in regard to ancient and heroic narratives, but in regard to events of very recent occurrence, to relate as a possible thing that Plato was the son of Amphictione, Ariston being prevented from having marital intercourse with his wife until she had given birth to him with whom she was pregnant by (the god) Apollo." [Origen (circa 185 CE) writing in Against Celsus 1, 37].
As far back as the first century of the common era Jews tried to correct Christians on "virgin" in Isaiah 7. Justin Martyr (100 CE, so VERY EARLY Christian) wrote in "Trypho the Jew" that Jews of his era said: "You (Jews) and your teachers venture to affirm that in the prophecy of Isaiah it is not said, 'Behold, the virgin shall conceive,' but, 'Behold, the young woman shall conceive, and bear a son."
But the status of the young woman in Y'shayahu / Isaiah 7:14 actually has nothing to do with the prophecy (whether she is a virgin, or not -- pregnant or not). It is a side issue at best.
By focusing on the word ha-al'mah (the young woman) missionaries are obsessing over the wrong word. The focus should be on the next word in the verse -- הָרָה harah. It is easy enough to debunk the virgin birth "prophecy" claim of Y'shayahu / Isaiahwithout focusing on the word הָעַלְמָה ha-al'mah (the young woman).
In Y'shayahu / Isaiah 7:14. הָרָה harah is the adjective "pregnant." (not "will conceive"). The words הִנֵּה הָעַלְמָה הָרָה hinneh ha-almah harah mean "there [pointing to her] is a pregnant young woman"
Since Isaiah was literally pointing out a pregnant woman to King Ahaz 700 years before Jesus this prophecy has nothing to do with Jesus or the messiah being "born of a virgin." הָעַלְמָה ha-al'mah (the young woman) says nothing about the young woman being a virgin or not being a virgin (although most pregnant women are not virgins).
Leaving , mistranslated as "virgin." (הָעַלְמָה ha-al'mah) untranslated, save for noting that the prefix ha- (which is normally the definite article "the") is being used here with poetic license in the sense of the demonstrative pronoun "that", lending emphasis to "that al'mah over there", i.e. the "al'mah" the prophet was pointing to as he spoke.
The words in question are הָרָה harah and וְיֹלֶֽדֶת v'yoledet.
The word : וְיֹלֶֽדֶת / v'yoledet (the fourth word in the prophet's statement) is the feminine singular present participle of the root ילד (to give birth), and means "[she] is giving birth"....
If the woman is about to give birth in front of Ahaz and Isaiah how can this be a prophecy about Jesus who would not be born for another 700 years?
Isaiah is saying literally: "she is about to give birth [at any moment]", and used the present participle just to indicate immediacy. The word after v'yoledet, i.e. בֵּן / bén, simply means "a son of."
If the prophecy has nothing to do with the young woman, what is the prophecy about (and who is it for)? Remember that prophecies are always for the current generation (and Isaiah lived 700 years before Jesus).
To understand the prophecy of Y'shayahu / Isaiah 7:14 read the chapter starting with the first line. The chapter is a warning to King Ahaz of Judah (who lived 700 years before Jesus). Isaiah tells King Ahaz that he needn't fear the two kings he is worried about.
Talking to King Ahaz the prophet Isaiah points to a pregnant young woman in the room and tells King Ahaz that before the unborn child is very old the two kings feared by Ahaz will be defeated. THIS is the prophecy. I could go into length to explain that the Hebrew is speaking of a pregnant woman, not a virgin who will have a child -- but that is really not important. (That must be quite a shock to missionaries!). Virgins get pregnant all the time -- and it is even possible for a virgin to get pregnant without intercourse. That is NOT the prophecy.
Knowing the background (King Ahaz is worried that he may be defeated by two kings and the prophet assures him that there is nothing to worry about) read on: "Therefore, HaShem, of His own, shall give you a sign; behold, the young woman is with child, and she shall bear a son, and she shall call his name Immanu'el. Cream and honey he shall eat when he knows to reject bad and choose good. For, when the lad does not yet know to reject bad and choose good, the land whose two kings you dread, shall be abandoned." Y'shayahu / Isaiah 7:14-16
As the missionary: "Which two kings did Jesus dread?
Ask the missionary: "Which lands of those two kings were abandoned during Jesus' lifetime"?
The answers are of course: none and none.
What of the child who is to be born in Y'shayahu / Isaiah 7:14-16? The importance was not his birth, but the fact that before the child was very old those two kings would be destroyed. Again, this is in the text: "Cream and honey he (the child) shall eat when he knows to reject bad and choose good. Y'shayahu / Isaiah 7:15. By the time the child is eating solid food (not just breast milk) and knows the difference between good and bad behavior those kings will be gone.
The prophecy of Y'shayahu / Isaiah 7 is fulfilled in Melachim Beit / II Kings 16. Those two kings are indeed defeated as Isaiah foretold Read Melachim Beit / II Kings 16:5 "Then Rezin the king of Aram and Pekah the son of Remaliah the king of Israel, went up to Jerusalem to wage war, and they besieged Ahaz, but could not wage war [with him].. . "
Ahaz, the very king of Y'shayahu / Isaiah 7 for whom Isaiah is making the prophecy saw the rulers Rezin and Pekah be destroyed - just as Isaiah prophesied in chapter 7: "the land whose two kings you dread, shall be abandoned." Y'shayahu / Isaiah 7:16.
Thus the prophecy Isaiah made for King Ahaz in chapter 7 is fulfilled in Ahaz' lifetime. It has nothing to do with virgin births, or virgins, or the messiah. King Ahaz lived 700 years BCE. If the sign was for him (as G-d Himself said). Given those facts (and they are all stated in Y'shayahu / Isaiah 7) then how could this be a prophecy that Jesus would be born from a virgin?
King Ahaz had been dead 700 years before Jesus -- so Jesus' birth could in no way be a sign for King Ahaz! In other words this is a VERY SPECIFIC prophecy for one person (Ahaz) and trying to fit it to another (Jesus) is deceit and nothing more.