μονογενής (monogenés)
Monogenes is a word of the Greek New Testament that occurs 9 times, whose meaning is contentious because of the Arian vs Trinitarian controversy. The contention is best illustrated by its translation in the earliest version, Jerome’s Vulgate of 400 AD.
- 3 times it applies to a parent’s only child (Luke 7:12, 8:42, 9:38) and is translated “unicus”, unique.
- once it is used to describe Isaac (Heb 11:17) and is translated “unigenitus”, only begotten.
- 5 times it is used to describe Jesus (John 1:14, 18, 3:16, 18, 1 John 4:9) and is translated “unigenitus”, only begotten.
Thus, the Vulgate (both Jerome and Clementine texts) adopted an uneven practice when rendering monogenes which was followed by Tyndale, the KJV, NKJV and many more until the late 20th century. Many modern versions since the late 20th century including NIV, NRSV, ESV, etc, uniformly translate this word as “only”, “unique” or equivalent.
The point at issue here is the cognate root of the second part of the word – is it related to gennao (beget, bear), or to genos (class, kind)? Modern linguistic analysis is firmly of the view that the latter is correct. Indeed, if the New Testament writers had intended “only begotten” then they would have used the word, monogennetos; but they did not. This conclusion is further shown in other instances of monogenes in the LXX such as Ps 21:21 (LXX)/ 22:20 (NASB), Ps 24:16 (LXX)/ 25:16 (NASB) where the meaning (in those cases) cannot be “only begotten”. The correct meaning is thus, "
only one of its kind within a kind or class or relationship" (BDAG).