Several parts combine into one character.

The traditional 壽 originated as a pictograph of an elderly figure: long flowing hair, a slightly bent posture, hand on a walking staff. From this depiction of advanced age grew the meanings: long-lived → long life → vital span → congratulatory wishes for long life. Japan and Mainland China both simplified to 寿; Korea retains 壽. Few characters carry as much ceremonial weight: 壽 / 寿 hangs on banners at every major birthday celebration in CJK cultures, especially the 60th and 70th milestone birthdays.

Korean reading "su." 長壽 (jangsu, longevity), 壽命 (sumyeong, lifespan), 無量壽 (muryangsu, "immeasurable life" — Buddhist term referring to Amitabha Buddha's eternal life-span; 무량수전 a temple hall dedicated to Amitabha), 萬壽無疆 (mansu-mugang, "ten-thousand longevities without limit" — formal birthday wish to elders, especially royals and dignitaries: "may you live ten thousand years"), 還甲壽宴 (hwangap-suyeon, 60th birthday banquet). Korean elder-respect culture is dense with 수 vocabulary.

Mandarin shòu, 4th tone. 寿 (shòu), 寿命 (shòumìng, lifespan), 长寿 (chángshòu, longevity), 寿星 (shòuxīng, "longevity star" = the guest of honor at a birthday celebration / the Daoist god of longevity), 祝寿 (zhùshòu, "to celebrate longevity" = to honor an elder's milestone birthday). Chinese birthday banquets feature 长寿面 (chángshòu miàn, "longevity noodles") — long uncut noodles symbolizing extended life.

Japanese on-reading ジュ (ju) — 寿命 (jumyō, lifespan), 長寿 (chōju, longevity). Kun-reading ことぶき (kotobuki, "auspicious congratulations / felicitations") — 寿 alone reads as kotobuki and serves as a generic word for "celebration / blessing." The character 寿 appears on Japanese New Year decorations and wedding gifts. Most charmingly: 寿司 (sushi) — the global Japanese culinary export — uses the same character 寿. The compound 寿司 was originally written 鮨 or 鮓 (with the fish radical — "fermented fish dish"), but Edo-period sushi vendors began using 寿司 as a more auspicious-looking ateji (kanji-substitution): "司 (sushi/sji) of 寿 (kotobuki, blessing)" — sushi as a "blessed dish." The kanji is purely phonetic, not semantic, but the propitious meaning made the substitution stick.

Memory aid: an elderly figure with long hair and a staff — long life, longevity, blessing.