The definition of both is one and the other one.
(adjective)An example of both used as an adjective is in the sentence, "I had the cheesecake and chocolate mousse; both desserts were tasty," which means that the cheesecake and the chocolate mousse were tasty.
Both means the one and the other one.
(pronoun)An example of both used as a pronoun is in the sentence, "The children played outside; both had an excellent time," which means that the children had an excellent time.
Both is defined as each of two parts or persons.
(conjunction)An example of both used as a conjunction is in the sentence, "Both girls and boys were invited to the birthday party," which means that boys and girls were invited to the birthday party.
See both in Webster's New World College Dictionary
adjective, pronoun
Origin: ME bothe < OE ba tha, both these < ba, fem. nom. & acc. of begen, both + tha, nom. & acc. pl. of se, that, the: akin to ON bathir, OS bethia, MDu bede, Ger beide: see ambi-
conjunction, adverb
See both in American Heritage Dictionary 4
adjective
Origin:
Origin: Middle English bothe
Origin: , probably from Old Norse bādhar
. Usage Note: Both indicates that the action or state denoted by the verb applies individually to each of two entities. Both books weigh more than five pounds, for example, means that each book weighs more than five pounds by itself, not that the two books weighed together come to more than five pounds. Both is inappropriate where the verb does not apply to each of the entities by itself. • In possessive constructions of both is usually preferred: the mothers of both (rather than both their mothers); the fault of both (rather than both their fault or both's fault). • When both is used with and to link parallel elements in a sentence, the words or phrases that follow them should correspond grammatically: in both India and China or both in India and in China (not both in India and China).Learn more about both