以为
yǐwéi · HSK 2
think/believe/consider erroneously
💭 以为 = take/use (以) + think (为); to take something as true — often wrongly
以 means 'take/use/by means of' and 为 means 'do/be/think'. Together: to take-as, to deem. Usually flags a mistaken belief: 我以为 = I thought (but was wrong).
以 — phonetic 㠯 (plow/tool) + 人 (person)
Originally a pictograph of a hand-held plow or tool (㠯), later combined with 人 (person) to suggest 'using' something. The core meaning 'to use' extended metaphorically to 'by means of', 'with', and 'because of'. In modern Chinese it functions mainly as a grammatical particle.
为 — simplified form of 為; from 爪 (claw/hand) over 象 (elephant)
The traditional form 為 originally depicted a hand leading an elephant, suggesting the act of doing or making work. Over time it generalized to mean 'to do, to act, for the sake of.' The simplified 为 preserves this 'do/for' meaning, with pronunciation shifting between wéi ('to be, to do') and wèi ('for, because of').