mitteregulaarseid

Mitteregulaarseid is a linguistic term used to describe irregular inflectional forms in languages that otherwise have regular paradigms. The word is formed in Estonian from mitte 'not' and regulaarne 'regular', and its plural form mitteregulaarseid is used to refer to irregular forms collectively. In grammar, the label applies across word classes—verbs, nouns, adjectives, and other parts of speech—where the form does not align with standard declension or conjugation patterns.

Irregular forms arise for various reasons, including historical sound changes, analogy, borrowing, or semantic irregularities. They can involve irregular verb stems, irregular plural nouns, irregular adjective comparisons, or irregular numerals. Some irregulars are fixed lexical items that recur across contexts, while others may be more limited to certain dialects, registers, or historical stages of a language.

In widely studied languages, irregularities are well documented across different domains. English, for example, has irregular verbs such as go–went–gone, irregular plurals like child–children, and some adjectives with irregular comparative forms like good–better. Other languages display irregularities in verb conjugations or noun declensions, often tied to historical developments or contact with other languages. Estonian, as a highly inflected language, exhibits relatively fewer irregular patterns than some Indo-European languages, but mitteregulaarseid forms still occur, particularly with loanwords or older native forms that resist standard inflection rules.

The study of mitteregulaarseid helps linguists describe a language’s morphology, informs language teaching by highlighting exceptions, and supports historical linguistics by tracing irregular forms to earlier stages of the language.