CJK Unified Ideograph-5FFD

It marks sudden change or careless disregard; the word around it decides. In 忽然, it marks an event as sudden; in 忽略 and 忽視, it marks something overlooked, ignored, or treated as unimportant.

The 忽然 vs 忽略 distinction is placement, not a different character: 然 turns the phrase toward suddenness, while 略 makes it about omission. Add 視 and the phrase can carry a stronger social judgment.

where did 忽 come from?

Its earliest identified evidence is late Warring States. The character appears in a late Warring States bronze inscription, with a matching small-seal form. Its earliest dictionary gloss is “forget”: 心 supplies the meaning and 勿 the sound, so it evolved as a sound-plus-meaning writing rather than a one-off invention.

Classical usage extends it to sudden, brief change. In contemporary Mandarin, that split survives as 忽然 for suddenness and 忽略 or 忽視 for disregard. Japanese lexicography preserves both senses and lists 忽 as the source form of 惚.