I so hate being pedantic, Hermanntrude, but you asked for it!
A copula verb is a "linking" or "state of being" verb. It links the subject with the subjective completion - either a noun or adjective. As examples:
Igor is huge.
Jane smells good (not goodly).
Gawd is great (not greatly)
Hades does not taste sweet, It tastes like hell!
In some languages "is" is absent in the present tense. One might say Igor - huge!
You bored yet?
And so, when the issue arose that "is" should not be, I was reminded that in some languages is isn't.
Sorry, but my sister dropped me as an infant!