The tiger-stripe radical — the cap component of 虎. A pure structural slot indexing characters built on the tiger's head/pelt motif: 虎 (tiger), 虑 (consider), 虚 (empty), 虐 (cruel), 虔 (pious). Not standalone in modern Chinese; appears only at the top of compounds, where it visually flags 'something tiger-related or tiger-shaped'.