Several parts combine into one character.

座 is a phonetic-semantic compound: 广 (the "sloped roof" radical, indicating a covered structure) + 坐 (zuò, "to sit" — itself a compound ideograph showing two people sitting facing each other on the ground). 坐 already meant "to sit" (the action), and 座 was created by adding the roof radical to specify a sitting place — a covered seat, an institutional position, a theater seat. The split is verb vs noun: 坐 is the action of sitting, 座 is where one sits or the position one occupies.

Korean reading "jwa." 座席 (jwaseok, seat), 座右銘 (jwaumyeong, "right-side motto" = a personal motto; the term comes from the ancient practice of placing an inscription beside one's seat as a daily reminder), 王座 (wangjwa, throne), 星座 (seongjwa, constellation — "star-seat"), 上座 (sangjwa, the seat of honor at a banquet table), 講座 (gangjwa, lecture / academic course).

Mandarin zuò, 4th tone. 座 (zuò, seat / place), 座位 (zuòwèi, seat — "seat-position"), 讲座 (jiǎngzuò, lecture series), 星座 (xīngzuò, constellation — Chinese zodiac signs are also called this in casual contexts: 星座 has expanded to include Western astrological signs). And critically: 座 functions as a measure word in Mandarin for large permanent structures — 一座山 (yī zuò shān, "one mountain"), 一座桥 (yī zuò qiáo, "one bridge"), 一座城市 (yī zuò chéngshì, "one city"). The grammaticalization of 座 as a noun classifier for monumental fixed objects is unique to Mandarin among CJK languages.

Japanese on-reading ザ (za) — 座席 (zaseki, seat), 座談 (zadan, discussion / round-table talk), 王座 (ōza, throne), 講座 (kōza, lecture course / academic chair). Most culturally distinctive: 正座 (seiza, "correct sitting" = the formal Japanese posture of kneeling with feet tucked beneath the buttocks, used in tea ceremony, Zen meditation, and traditional dining; physically demanding for the unaccustomed). Kun-reading すわる (suwaru, to sit) — 座る (suwaru), 座らせる (suwaraseru, to make someone sit / seat someone). 座席に座る (zaseki ni suwaru, "to sit in a seat") shows both readings cooperating.

Memory aid: a roof (广) over two people sitting (坐) — the place where one sits.