衣 is a pictograph showing the upper garment of ancient Chinese clothing — a robe with the collar at the top and sleeves spread to either side. From oracle bone times the silhouette of an unfolded jacket has been clearly visible in the character. As a radical, 衣 morphs into the compressed form 衤 (the "clothing radical" used on the left side of compounds) and anchors a vast vocabulary of garment-related characters: 装 (decorate / outfit), 裙 (skirt), 袋 (pouch / bag), 袖 (sleeve), 裸 (naked), 補 (mend). Where 服 emphasizes the act of wearing and submitting, 衣 names the garment itself.

Korean reading "ui." 衣服 (uibok, clothing — formal pairing of both clothing characters), 衣裳 (uisang, attire / costume — used theatrically), 上衣 (sangui, upper garment / top), 下衣 (haui, lower garment / bottoms), 浴衣 (yokui, bathrobe / yukata when adopted from Japanese), 白衣 (baekui, "white robe" — the traditional dress of Korean medical staff and academic researchers; also the symbolic name "angel in white" for nurses). Korean often pairs 衣 with 服 in formal compound 의복, and uses pure hangeul 옷 in everyday speech.

Mandarin yī, 1st tone. 衣 (yī, clothing), 衣服 (yīfu, clothes — everyday word), 上衣 (shàngyī, top / shirt), 内衣 (nèiyī, underwear), 大衣 (dàyī, "big clothing" = overcoat), 毛衣 (máoyī, "wool clothing" = sweater), 雨衣 (yǔyī, raincoat). Mandarin's vocabulary for garment types is built almost entirely from 衣 + a modifier — adjective + 衣 generates clothing names productively.

Japanese on-reading イ (i) — 衣服 (ifuku, clothing — formal), 衣装 (ishō, costume / theatrical outfit), 衣食住 (ishokujū, "clothing-food-dwelling" = the three essentials of life — a key Japanese concept in lifestyle and philosophy). The famous Japanese garment 浴衣 (yukata, the casual cotton summer kimono worn at festivals and traditional inns) reads with the irregular jukujikun reading: 浴衣 → ゆかた, neither pure on nor kun. Kun-reading ころも (koromo) — 衣 (koromo, robe / Buddhist priest's robe / the coating on tempura). The compound 天ぷらの衣 (tenpura no koromo, "the koromo of tempura") refers to the light flour-and-water batter coating tempura — comparing the crispy shell to a robe. Japanese cuisine extends the clothing metaphor to food coatings.

Memory aid: an upper garment with collar and sleeves spread out — the original silhouette has been preserved across three thousand years.