In some of the Romance languages the copula, the equivalent of the verb to be in English, is relatively complex compared to its counterparts in other languages. A copula is a word that links the subject of a sentence with a predicate (a subject complement). Whereas English has one main copula verb (and some languages like Russian mostly express the copula implicitly) some Romance languages have more complex forms. As the Romance languages developed over time, the three separate Latin verbs became just one or two verbs in the Romance languages.