Both and Either

Both adjective - (used with count nouns) two considered together; the two.

Either and both are semantically related. In some cases you can use "Either" instead the word "Both" as a pronoun or an adjective or an adverb.

Either adverb - In addition to what has been said.

Both and either are semantically related. You can use "Both" instead the word "Either" as an adjective or an adverb or a pronoun or a determination.