When you sing, you make musical sounds with your voice, usually producing words that fit a tune.
例句
I can't sing...我不會唱歌。I sing about love most of the time...我大多唱愛情歌曲。
(鳥類或昆蟲)鳴叫，啼，啁啾，啼囀
When birds or insects sing, they make pleasant high-pitched sounds.
例句
Birds were already singing in the garden.小鳥已經在花園里歌唱了。
(尤指同一組織里的人)口徑一致，意見一致
If you say that people, especially people in the same organization, are singing from the same hymn sheet or are singing from the same song sheet, you mean that they are saying the same things in public about something and appear to agree about it.
例句
We should bring together the departments so that we're all singing from the same hymn sheet.我們應該把各部門聯合起來，這樣我們就能意見一致了。