From Sino-Korean 必要 (필요), composed of 必 (필, *bì* — "must, certainly") and 要 (요, *yào* — "need, want, essential"). The same hanja compound is used in Chinese (必要, *bìyào*) and Japanese (必要, *hitsuyō*), all carrying the shared meaning of "something that must be had."

In Korean, 필요 most commonly appears in the pattern **[noun]이/가 필요하다** ("to need [noun]"), where 필요하다 functions as an adjective-verb. This is a key structural difference from English: Koreans say literally "help is necessary to me" rather than "I need help." Confusing this with the English "need" verb pattern is a common early-learner mistake.