百分比 (bǎi fēn bǐ) is the standard term for 'percentage' — a value out of 100 (e.g., 50%). 占比 (zhàn bǐ) refers to the proportion or share a part occupies within a whole, while 比重 (bǐ zhòng) also means proportion but can additionally mean 'specific gravity'. 百分点 (bǎi fēn diǎn) is a distinct term meaning 'percentage point', used for differences between percentages.