to undo a lock; to unlock

(education, language learning) listening comprehension

to understand spoken language that one hears

(historical) Japanese-language annotation of Chinese-language works / (historical) Korean-language annotation of Chinese-language works

optimal solution

(collective) brothers / (collective, by extension) siblings / (collective, by extension) brothers and sisters; brethren (brotherhood; fellowship)

one's parents and brothers and sisters; one's nearest relatives

a magnifying glass

(anatomy) a pectoralis major muscle

study of something; the sum of knowledge accrued by scholars; the realm of refined learning; scholarship