needed in order to achieve a particular result

He lacks the necessary skills for the job. 他不具备做这项工作所需的技能。

I don't have much time so I won't be staying any longer than necessary. 我时间不多，所以若非必要我不会逗留。

Just do what's necessary and then leave. 做完必要的事情就走吧。

If necessary, we can always change the dates of our trip. 必要的话，我们随时可以改变旅行的日期。

Is it necessary for all of us to be present at the meeting this afternoon? 我们必须全体出席今天下午的会议吗？

We don't want to take any more luggage with us than is strictly necessary. 除了必不可少的行李以外，我们不想带多余的东西。

used in negatives and questions to show that you disapprove of something and do not think it should be used or done

I don't think that kind of language is necessary in a show that kids could be watching. 我真的认为在电视上使用那种语言是不可取的。

Was it really necessary for you to say that? 你非得那样说吗？