Abstract: The present article deals with the verb with the verb to be in Old Bulgarian and Old English. Comparing the verb’s lexical meanings and grammatical uses we assume that the forms derived from the root *es were originally used to express existence and identity, and the forms of the roots *bhV and *h₂wes- were only used to express existence. Later, the idea of existence united *bhV and *es into a single paradigm. The formal opposition of roots becomes a means of expressing different grammatical categories of the verb. It is clearly visible that there exist similarities in the lexical and grammatical functions of the verb to be in Old Bulgarian and Old English.
Key words: copula, full verb, identity, existence, lexical meaning, grammatical meaning