16 For thus God loved the world that He gave His only begotten Son that everyone believing in Him may not perish, but have life eternal. John 3:16 (translated from the NA28 Greek text)
There are many great truths in John 3:16 such as God’s love (ἀγαπάω (agapaō)) for His own, and the eternal life that comes by faith (πιστεύω (pisteuō)) in Christ, it is strikingly unique because the apostle John is the only Scripture writer who uses the term μονογενής (monogenēs) to describe the relationship of Jesus to the Father. Several modern translations (ESV, NRSV, NLT, CEV, and GWT) replace “only begotten” with “only” or “one and only” (NCV and NIV). Such readings however, clearly do not mean the same thing as “only begotten,” so, which is correct, or does it really matter?
Monogenēs is a compound comprised of μόνος (monos), “only, alone, without others,” and γένος (genos), “offspring, stock.” The clear idea then is “only offspring,” “only physical stock,” or “only born-one.” In ancient Greek, this word was used to refer to a unique being.