Several parts combine into one character.

In oracle bone script, 喜 shows 壴 (a drum on a stand) above 口 (a mouth). The picture is unmistakably festive — a drum beats and a mouth opens to sing. Joy in ancient China was depicted as the percussive, vocal celebration of a feast. The character carries the energy of communal celebration rather than private contentment.

In Chinese culture, 喜 carries enormous symbolic weight. Doubled into 囍 (the "double happiness" character), it becomes the most auspicious symbol at weddings — pasted on doors, embroidered on bedding, printed on every red envelope and decoration. No equivalent symbol exists in Japanese or Korean wedding culture; this doubling is uniquely Chinese.

Korean reading "hui." 歡喜 (hwanhui, great joy / rejoicing), 喜悲 (huibi, joy and sorrow), 喜劇 (huigeuk, comedy), 喜消息 (huisosik, "joyful news"). Korean uses 喜 in formal compounds; everyday "happy" is the native (gippeuda).

Mandarin xǐ, 3rd tone. Workhorse of the joy lexicon: 喜欢 (xǐhuan, "to like / be fond of") is one of the highest-frequency verbs in spoken Chinese — children learn it immediately. 欢喜 (huānxǐ, delighted), 喜悦 (xǐyuè, happiness), 恭喜 (gōngxǐ, "congratulations" — used at weddings, births, New Year), 喜事 (xǐshì, "happy occasion" = wedding). Modern Chinese keeps 喜 actively in daily speech in a way Korean and Japanese do not.

Japanese on-reading キ (ki) — 歓喜 (kanki, exultation), 喜劇 (kigeki, comedy). Kun-reading よろこぶ (yorokobu, "to rejoice") and the noun form よろこび (yorokobi, joy) are used in everyday speech: お客様に喜んでいただく ("to please our customers"). Japanese 喜ぶ tends to be used about a gladness that someone else recognizes or causes, more relational than self-contained.

Memory aid: drum (壴) + mouth (口) — the music and song of a feast.