"Fusional" refers to a type of linguistic structure where multiple grammatical categories are combined into a single affix. In fusional languages, a single morpheme can express various grammatical functions, such as tense, mood, and number. This contrasts with agglutinative languages, where each grammatical function is represented by a separate affix. An example of a fusional language is Latin, where a single verb form can indicate the subject, tense, and mood simultaneously. This complexity allows for more compact expressions but can make the language more challenging to learn due to the intricacies of its inflections.