Okay, let's look at John 3;16. There are several issues involved in this text, one of which deals with the Greek word
MONOGENHS. The word can carry different meanings. For instance,
MONOGENHS is used of Isaac, Abraham's son in Josephus,
Antiquities, 1:222) and is used in the sense of "only." For two examples of
MONOGENHS referring to an "only son" consider Luke 7:12 and 9:38. So also the use of
MONOGENHS as the "only" daughter of Jairius (Luke 8:42).
In John's use of the word,
MONOGENHS seems to carry the sense of "Only One" or as some prefer "only-begotten," who emphasize the
GENNHSQAI "begotten of God" in John 1:13. This would be similar to Paul's use of
PRWTOTOKOS "first-born" of Romans 8:29 and Colossians 1:15). But even the root of the word
MONOGENHS is debated. In John's writings,
MONOGENHS is only used in reference to Jesus, so even in John's context, the sense of "unique" is a given.
So, which is correct? Well, they both are. In a sense, this is a case in which the KJV ("only begotten") could seem to be narrower (more restrictive) than some other translations.
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But that never stopped me from understanding the KJV. In fact, I used to be more confused when I used an NASB.
Again, I would be interested in those passages that you claim are more confusing in the NAS.
Actually the reading level for both NAS and KJV are about the same. So, confusion with one most likely means confusion with the other. Or it seems that you just have a
preference for the KJV - which is fine, as long as someone doesn't take this to mean that the KJV is the better, or the only reliable translation.