en_tn/pro/20/15.md

lips of knowledge are a precious jewel

This speaks of the value of lips of knowledge by comparing them to a precious jewel. AT: "lips of knowledge are as valuable as an expensive jewel" (See: rc://en/ta/man/translate/figs-metaphor)

lips of knowledge

Here "words" are referred to as "lips." AT: "wise words" or "words of knowledge" (See: rc://en/ta/man/translate/figs-metonymy)