世 appears in key words: 世界 (world), 世纪 (century), 一辈子/一世 (a lifetime). It's rarely used alone in modern Chinese.
Components
ideograph
世shì
generation; era; world
Five-stroke unitary symbol carrying 'generation, age, world' as a single fused shape. Doesn't separate cleanly into independent components in the modern silhouette. Indexed under Kangxi #1 一 via the top horizontal; no further radical-element is visibly present. Historically three 十 joined at the base - thirty years, one generation.
Filed under radical 一 (yī, #1) by convention. 一 is not a separate component in 世, so no strokes are highlighted.
