In John 1:14, 18, the Greek term translated as “only begotten” is monogenes. Only John uses this adjective to describe Jesus, and he uses it five times. Its most common usage in Greek is as a term of endearment, though that is not all it adds to Jesus' standing before humanity. The way John uses it also specifically indicates a human family relationship.
It also carries the sense of “only,” intensifying the sense of endearment with the idea of singleness or uniqueness. Thus, the sense of “only” becomes an important addition. There are no others like Him, and Scripture adds that there never has been. He is unique even in respect to all other usages of “son of God” in the Bible. He stands alone. Our Savior has no competition.
At this point, we need to grasp a simple, Greek grammatical rule that most English-speakers are not normally exposed to. In Greek, ho is the equivalent of the English definite article “the.” However, the apostle John does not place ho before “only begotten” in verse 14, nor before “Father” in verse 18 (though most English translations supply it anyway). Its absence is legitimate in Greek usage, as it intensifies the descriptive power of the term “only begotten”—and thus what John is attempting to explain. It amplifies its power.
By writing it in this manner, John specifically signifies that Jesus is the single, sole, exclusive, only representative and—this is important—character (image) of the Being, the Father, who sent Him. This lays additional, greater glory upon the characteristics revealed about Jesus in context.
The apostle's object was to demonstrate and emphasize as best he could through mere words the height of the level of glory he and his fellow apostles witnessed in their three-and-a-half-year relationship with Jesus. With words, He severs Jesus of Nazareth, son of Joseph and Mary, from all other set-apart sons of God in the Scriptures, as well as from any kind of earthly, human, generational relationship.
Essentially, he is stating that Jesus' relationship with the Father was unoriginated. All human relationships are originated and continue through the pairing of a father and a mother. Jesus' relationship with the Father was not so. There is nothing we humans could conceive of as a sexual act by the Father that produced Jesus.
This reality should have a major impact on how we understand Their unity. Recall that Jesus says in John 10:30, “I and My Father are one.” Therefore, everything the Father is in character Jesus is also, even though Jesus is a separate personality from the Father. Just as the Father has always existed, so has the Son. The apostle John used this grammatical rule five times, so we would get the point. Jesus was and is every bit as much God as the Father.
Thus, the term “begotten” as used regarding Jesus does not apply in the same way it does for humans. Nevertheless, John used it to establish the concept of a family relationship so we could understand our relationship to God, as Father and child, more clearly.
