He decided to turn professional.

他决定转为职业人员。

《牛津词典》

After winning the tennis competition, Jackson decided to turn professional, and was soon winning a lot of money in international competitions.

杰克逊赢得那次网球比赛以后，决定转为职业运动员，结果很快就在国际比赛中赢了很多奖金。

youdao

Instead of going to college, he chose to turn professional and in 1996 became the youngest player ever to join the NBA.

他没有上大学，而是选择了去当一名职业选手。在1996年，他成了nba里有史以来最年轻的球员。

youdao

The decision by the 15-year-old golfer to turn professional comes just before she turns 16 on Oct. 11.

FORBES: Magazine Article

With that kind of money on offer, it is not surprising that some old hands have decided to turn professional.

ECONOMIST: Where there��s MUD, there��s brass

My enjoyment is working with this talent, seeing them reach their potential and then making that choice (whether to turn professional).

BBC: Edwards upbeat despite defections