while but 表示转折如何区分

while和but都有转折的意思，但是表示转折的意思时，while同时含有表对比的意思；While作并列连词用，意思为“而，然而”，表对比。而but表转折。

Some people waste food while others haven\'t enough.

有些人很费粮食，然而有些人却吃不饱。

while这里即表示对比有表示转折！

The son was having a good meal at home，while the parents were working in the fields.

儿子在家吃好饭而父母却在田里辛勤劳作。

I ought to have helped her，but I never could.

我本该帮她但没能。