This is the 17404th most frequent Russian word.
теннис
Tennis.
Here, 'теннис' is used as the name of the sport 'tennis'.
Я люблю играть в теннис.
I love playing tennis.
In this sentence, 'теннис' refers to the sport for which the racket will be used.
Моя сестра купила новую ракетку для тенниса.
My sister bought a new racket for tennis.
Here, 'теннис' is used in a broad sense as the activity or concept of tennis as a form of exercise.