Copula Vs Auxilary
Copula vs auxiliary verbs
What is the difference between auxiliary and copula? Copula verbs are usually called linking verbs, which LINK the (simple) subject to a noun or an adjective in the predicate. Forms of BE, or "to be" verbs, can also be used as auxiliary verbs: She IS sleeping. The main verb is SLEEPING; the word IS is an auxiliary verb.
auxiliary verb
assists the main verb; primary ones 'do', 'have' and 'be' denote changes of tense
Copula
when the verb be or any of its derivatives serve as the main verb in a sentence
Brown's Grammatical Morphemes
when toddlers use 2 and 3 words together they begin using grammatical morphemes. A morpheme is something that changes the words (prefix, suffix, the word itself)