turning point
noun [ C usually singular ] uk/ˈtɜː.nɪŋ ˌpɔɪnt/ us/ˈtɝː.nɪŋ ˌpɔɪnt/
转折点，转机
the time at which a situation starts to change in an important way
The organization called the new regulations a turning point in the campaign against smoking. 该组织称这些新规定是禁烟运动的转折点。
The turning point in her political career came when she was chosen to run for a Senate seat. 她被推选参加竞选参议院议员，这成为她政治生涯的转折点。