假使
jiǎshǐ · HSK 7
if
假 (suppose) + 使 (cause/make) = supposing it causes... = if, in case
假 is the same suppose-character in 假如 and 假设, the family of if-words; 使 means to cause or make. Together they set up a hypothetical: supposing that X causes Y. Note the falling-rising tones jiǎshǐ, both third tone.
假 — person radical 亻 + 叚 (borrow)
假 combines the person radical 亻 with 叚, which originally meant 'to borrow' and provides the sound. The core idea is a person borrowing something, which extended to 'borrowed,' 'not real,' or 'fake.' From there it also developed the meaning 'leave/vacation' (time borrowed away from work).
使 — person radical 亻 + official 吏
Originally a phono-semantic compound: 亻 (person) gives the meaning and 吏 (official, also a phonetic clue) suggests the sound. The early sense was 'to send a person on a mission,' from which came 'envoy/messenger' and the broader meanings 'to use' and 'to cause/make.'