症

It is a phono-semantic compound character,

formed by combining:

疒 (“sick radical,” meaning “illness, sickness”) for meaning, and

正 (“correct,” jeong) for sound.

Originally, this character was a simplified form of 證 (증거 증).

證 basically meant “evidence,” but from that meaning it also carried the sense of “signs of illness” or “symptom.”

When used in this medical sense, people conventionally wrote it as 症.

Because of this, many premodern Chinese dictionaries – including the Kangxi Dictionary (강희자전) – did not list this character.

Later, in modern times, 症 became completely separated from 證 and gained an independent status.

症勢 - symptom state

症狀 - symptoms