Several parts combine into one character.

The traditional 輕 is a phonetic-semantic compound: 車 (cart / vehicle) on the left provides the meaning, while 巠 (jīng, originally a pictograph of warp threads on a loom) on the right provides the sound. The original meaning was specifically "a light cart" — a quick, unburdened vehicle as opposed to a freight wagon. Japan and Mainland China both simplified the right component, producing 軽 (Japanese shinjitai) and 轻 (Mainland simplified) — Korea retains the traditional 輕.

Like 重 (heavy), 輕 (light) carries weight in both physical and mental senses: light → unburdened → relaxed → frivolous / careless. The pairing is one of the cleanest opposites in CJK vocabulary.

Korean reading "gyeong." 輕重 (gyeongjung, "lightness and heaviness" = severity / gravity of a matter), 輕油 (gyeongyu, diesel fuel — "light oil," contrasting heavier petroleum products), 輕量 (gyeongnyang, lightweight — used in sports weight classes), 輕視 (gyeongsi, to take lightly / disregard), 輕薄 (gyeongbak, frivolous / shallow — applied to personality), 輕傷 (gyeongsang, minor injury). The semantic chain "physical lightness → carelessness → moral lightness" is fully active in modern Korean.

Mandarin qīng, 1st tone (simplified 轻). 轻松 (qīngsōng, "light-loose" = relaxed / easy / unburdened — extremely common in spoken Chinese), 轻视 (qīngshì, to look down on / disregard), 年轻 (niánqīng, young — literally "of light years"). The Mandarin compound 年轻 is uniquely Chinese: youth is conceptualized as the lightness of having few years to carry. Korean has (jeolda) and Japanese has 若い (wakai); only Mandarin equates "young" with "year-light."

Japanese on-reading ケイ (kei) — 軽傷 (keishō, minor injury), 軽量 (keiryō, lightweight), 軽視 (keishi, disregard). Kun-reading かるい (karui, "light") — 軽い (karui), 軽く (karuku, lightly). Japan's most distinctive use of this character is in the term 軽自動車 (keijidōsha, "light automobile" / "kei car") — a uniquely Japanese vehicle classification for cars under 660cc engine displacement, granted tax and insurance benefits, and shaped Japanese car design and urban driving culture for decades. Tiny boxy cars dominate rural Japan because of this category.

Memory aid: 車 (cart) + 巠 (loom warp threads — light, taut) — the original meaning was a lightweight unburdened vehicle.