In grammar, inflection or inflexion is the modification of a word to express different grammatical categories such as tense, mood, voice, aspect, person, number, gender and case. The inflection of verbs is also called conjugation, and the inflection of nouns, adjectives and pronouns is also called declension.An inflection expresses one or more grammatical categories with a prefix, suffix or infix, or another internal modification such as a vowel change.