Is the Copula the Only Irregular Verb in a Language?

The copula can be the only irregular verb in a language. In languages with extremely complex polypersonal verb marking, it will typically only be marked for the copula subject. Different parts of your inflectional system for your copula might actually have different historical sources. English does not allow this, although it's sometimes used in bad fantasy movies. Dogs are meaning their dogs or sometimes occurrence. These days many accidents are effectively many accidents happen.