"Wife" and "Fiancée"

[Odessa Dawn]

Do "Wife" and "Fiancee" have the same exact meaning? From my point of view, we can't call a female "Wife" until she consumes marriage. On the other hand, "Fiancee" as the dictionary defines it: "A woman who is engaged to be married."
Definition of fiancée | Collins English Dictionary
fiancée noun - definition in British English Dictionary & Thesaurus - Cambridge Dictionary Online
wife noun - definition in British English Dictionary & Thesaurus - Cambridge Dictionary Online

Question: Why is in the below text the word "Fiancee" completely different from what has been stated in the dictionary? Does this mean that the dictionary can't be relied on? Please set me free from the shackles of ignorance.

The Book of Luke Chapter 2
⁴And because Joseph was a descendant of King David, he had to go to Bethlehem in Judea, David's ancient home. He traveled there from the village of Nazareth in Galilee.
⁵He took with him Mary, his fiancée, who was now obviously pregnant.

In another version : (New King James Version)

⁴ Joseph also went up from Galilee, out of the city of Nazareth, into Judea, to the city of David, which is called Bethlehem, because he was of the house and lineage of David, ⁵ to be registered with Mary, his betrothed wife,^[a] who was with child.
Luke 2 NKJV - Christ Born of Mary - And it came to - Bible Gateway

betrothed noun - definition in British English Dictionary & Thesaurus - Cambridge Dictionary Online

In a word, according the above texts, "Wife" and "Fiancee" are interchangeable, aren’t they? And the dictionary failed to set me a proof that they are similar.

Thank you.

[emsr2d2]

People become "engaged [to be married]" before they actually get married. The engagement period can last from a few months to several years. When a couple decide that they want to marry, they get engaged first (he woman usually receives an engagement ring to wear on her ring finger). They might have an engagement party and receive cards and presents to congratulate them. Then, an unspecified amount of time later, they get married. This time they get a ring each to wear on their ring finger, and they have the wedding ceremony, a party (called a wedding reception), more cards and presents and then go on honeymoon.

That's the traditional way at least.

[SoothingDave]

"Betrothed" is the traditional way this is expressed in the Bible, as you have seen. The betrothal process was long in those days, as it often is today.

The point of the Bible story is that Mary was pregnant before she was married. Which would be evidence of sinful conduct in normal cases. There is a passage where Joseph contemplates quietly cancelling his marriage because of Mary's condition (which he did not cause). But an angel tells him to continue with his plan to marry Mary.

This was not a normal case, however, as Mary conceived Jesus in her womb "by the power of the Holy Spirit' and not by any action of man.