轮子
lún zi · HSK 4
wheel
☸️ 轮子 = wheel + suffix 子 (zi turns it into a noun)
轮 alone means wheel; the 子 suffix makes it a standalone noun, like adding -er or -ie in English. Compare 桌子 (table), 椅子 (chair) — same noun-forming 子.
轮 — car radical 车 + 仑 (phonetic)
轮 is a semantic-phonetic compound. The left side 车 (chē, 'cart/vehicle') gives the meaning, since 轮 originally referred to a wheel. The right side 仑 supplies the sound 'lún'. From 'wheel' it extended to related senses like 'rotate', 'take turns', and 'round'.
子 — pictograph of a baby/child with arms out
子 began as a pictograph of a swaddled infant with a large head and outstretched arms, originally meaning 'baby' or 'child.' From there it broadened to 'son,' 'offspring,' and a respectful suffix for masters like 孔子 (Confucius). It also became one of the twelve earthly branches.