曾 céng used to be
already; formerly; once; the past
céng (once; formerly) and zēng (great-grand) - 曾经 céngjīng once, 曾祖父 zēngzǔfù great-grandfather
How it came to be
A steamer seen from the side, pot below, tray with holes in the middle, steam on top. Layer on layer is the idea, and a layer over an earlier one means 'once'.
How it is used
- Almost always appears as 曾经 céngjīng, an adverb marking that something happened at some point in the past - 我曾经去过北京 wǒ céngjīng qùguo Běijīng, "I've been to Beijing before".
- 曾经 (céngjīng) is written/somewhat formal register; casual speech often just uses 以前 or the experiential 过 alone without 曾经.
- In writing, 不曾 (bùcéng) means has never, the same céng with 不 in front.
- Don't confuse this with 层 céng (floor/layer) - same pinyin, unrelated meaning.
- Read zēng it names family three generations away - 曾祖父 (zēngzǔfù) great-grandfather, 曾孙 (zēngsūn) great-grandson.