real tennis vs tennis

real tennis and tennis both are nouns.

Word	Noun	Adjective	Verb	Adverb
real tennis	Yes	No	No	No
tennis	Yes	No	No	No

As nouns, tennis is a hypernym of real tennis; that is, tennis is a word with a broader meaning than real tennis:

real tennis: an ancient form of tennis played in a four-walled court
tennis: a game played with rackets by two or four players who hit a ball back and forth over a net that divides the court

Other hypernyms of real tennis include lawn tennis.

real tennis (noun)	tennis (noun)
an ancient form of tennis played in a four-walled court	a game played with rackets by two or four players who hit a ball back and forth over a net that divides the court