Tra từ each - Từ điển American Heritage Dictionary 4th

each (ēch)adj.
Being one of two or more considered individually; every:
Each person cast a vote. My technique improved with each lesson.pron.
Every one of a group considered individually; each one.adv.
For or to each one; apiece:
ten cents each. [Middle English ech, from Old English ǣlc. See līk- in Indo-European Roots.]
Usage Note: The traditional rule holds that the subject of a sentence beginning with each is grammatically singular, and the verb and following pronouns must be singular accordingly: Each of the apartments has (not have) its (not their) own private entrance (not entrances). When each follows a plural subject, however, the verb and subsequent pronouns remain in the plural: The apartments each have their own private entrances (not has its own private entrance). But when each follows the verb with we as its subject, the rule has an exception. One may say either We boys have each our own room or We boys have each his own room, though the latter form may strike readers as stilted.·The expression each and every is likewise followed by a singular verb and, at least in formal style, by a singular pronoun: Each and every driver knows (not know) what his or her (not their) job is to be. See Usage Note at every. See Usage Note at they.