Important textual evidence may be cited (cf. p. 10) for omitting this word.
“Fornication,” that is, immorality in general, would, of course, include “adultery.”
Manifest.
The following catalogue of sins is illustrative rather than exhaustive. Sensuality, superstition, selfishness, and intemperance are all represented. As the Galatians forsook the guidance of the Holy Spirit these evil fruits doubtless appeared in their lives.
Works of the flesh.
That is, the deeds that result from the unrestricted operation of human passions, feelings, and desires. See on v. 16. Paul gives a partial list of these “works” in vs. 19-21.