Texas Ranger vs lawman

Texas Ranger and lawman both are nouns.

Word	Noun	Adjective	Verb	Adverb
Texas Ranger	Yes	No	No	No
lawman	Yes	No	No	No

As nouns, lawman is a hypernym of Texas Ranger; that is, lawman is a word with a broader meaning than Texas Ranger:

Texas Ranger: a member of the Texas state highway patrol; formerly a mounted lawman who maintained order on the frontier
lawman: an officer of the law

Other hypernyms of Texas Ranger include law officer, peace officer.

Texas Ranger (noun)	lawman (noun)
a member of the Texas state highway patrol; formerly a mounted lawman who maintained order on the frontier	an officer of the law