lawn tennis vs tennis

lawn tennis and tennis both are nouns.

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

As nouns, lawn tennis and tennis are synonyms defined as:

lawn tennis and 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

lawn tennis (noun)	tennis (noun)
a game played with rackets by two or four players who hit a ball back and forth over a net that divides the 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