This is the 9440th most frequent Japanese word.
空手
Karate: A traditional Japanese martial art focused on unarmed combat using punches, kicks, and defensive techniques.
In this sentence, '空手の大会' specifies '大会' (tournament) as being related to karate.
空手の大会で優勝するのが彼の夢です。
His dream is to win a karate tournament.
In this sentence, '空手' is used as a noun to denote the martial art itself.
空手は日本の伝統的な武道です。
Karate is a traditional martial art of Japan.
Here, '空手' functions as the object of the verb '学び始める' (to start learning).