以
yǐ · HSK 7
using
🔧 以 = by means of / using; seen in 可以 keyi (can) and 所以 suoyi (therefore)
The old form showed a person holding or using a tool, giving the sense of doing something by means of it. Now a core grammar word: 可以 = can, 所以 = therefore, 以前 = before, 以为 = to assume.
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.