Both is a word that expresses the concept of "two". There are several synonyms for the word both, some of which can be used interchangeably, while others have a slightly different meaning. Two, pair, couple, and duo are some of the most common synonyms for both, each conveying a similar idea of two entities. However, the word "twain" suggests two things that are different or separate, while "binary" implies a relationship of opposites. Other synonyms for both include twosome, dyad, double, and twin. Selecting the right synonym for both depends on the context of the sentence and the intended meaning of the text.