每 (měi) means every or each and is always used with a time word or measure word (每天, every day; 每个人, every person; 每次, every time). It does not stand alone and requires a following noun or noun phrase. 每 is often paired with 都 (dōu, all) in the predicate to reinforce universality: 每个人都要遵守规则 (every person must follow the rules). It contrasts with 各 (gè, each separately) which highlights individual differences.