This is the 4939th most frequent Japanese word.
硬式
"硬式" means "hard-type" or "official type," often referring to sports using hard balls, like "hardball" in baseball or tennis.
In this sentence, "硬式" refers to the type of tennis played with a hard ball, distinguishing it from soft tennis.
彼は硬式テニスを始めた。
He started playing hardball tennis.
Here, "硬式" is used to describe the form of baseball played with traditional hard balls, as opposed to rubber balls.
硬式野球を観戦するのが好きです。
I like watching hardball baseball.
In this case, "硬式" is used generally to denote activities or sports involving hard balls, requiring specific preparations or equipment.