Except in the case of inflexions, suffixes, on the other hand, nearly always change the grammatical class of the base to which they are added. The best way of classifying prefixes in English, therefore, is to classify them on the basis of their meaning, and the best way of classifying suffixes in English is to classify them on the basis of their grammatical function. Prefixes commonly used in the formation of English words can be semantically classified as