一边

一边 (yìbiān) has two main uses. First and most important, in the doubled construction 一边 V₁ 一边 V₂, meaning 'doing V₁ and V₂ at the same time' — this is THE Chinese way to express simultaneous actions, where English uses '-ing while' or 'as.' Examples: 一边吃饭一边看电视 ('eat dinner while watching TV'), 一边走一边说 ('talk while walking'). Both verbs must be things one person actively does. Second, as a noun, 一边 means 'one side' or 'aside': 站在一边 ('stand to one side'), 这一边 ('this side'). Pronunciation note: in the simultaneous-action structure, 一 takes the second-tone change rule — written yìbiān, sometimes you'll see yībiān in dictionaries, but say yì in fast speech. In casual speech, 边 is often unstressed (yìbian).

Note: Standard in speech and writing. The doubled structure 一边...一边... is one of the most common ways Chinese expresses simultaneous actions.

Memory hook: Two 一边s side by side = two parallel tracks of action, both running at the same time.