turning vs coming back

turning and coming back both are nouns.

Word	Noun	Adjective	Verb	Adverb
turning	Yes	No	No	No
coming back	Yes	No	No	No

As nouns, coming back is a hyponym of turning; that is, coming back is a word with a more specific, narrower meaning than turning:

turning: a movement in a new direction
coming back: the occurrence of a change in direction back in the opposite direction

Other hyponyms of turning include reversal, turn around, swerve, yaw, gyration, revolution, rotation, return, volution.

turning (noun)	coming back (noun)
the act of changing or reversing the direction of the course	the occurrence of a change in direction back in the opposite direction
act of changing in practice or custom
the activity of shaping something on a lathe
the end-product created by shaping something on a lathe
a movement in a new direction
a shaving created when something is produced by turning it on a lathe