Irregular verbs are those verbs that fall outside the standard patterns of conjugation in thelanguages in which they occur. The idea of an irregular verb is important in second language acquisition, where the verb paradigms of a foreign language are learned systematically, and exceptions listed and carefully noted. Thus for example a school French textbook may have a section at the back listing the French irregular verbs in tables. Irregular verbs are often the most commonly used verbs in the language.
In linguistic analysis, the concept of an irregular verb is most likely to be used in psycholinguistics, and in first-language acquisition studies, where the aim is to establish how the human brain processes its native language. One debate among 20th-century linguists revolved around the question of whether small children learn all verb forms as separate pieces of vocabulary or whether they deduce forms by the application of rules. Since a child can hear a verb for the first time and immediately reuse it correctly in a different tense which he or she has never heard, it is clear that the brain does work with rules, but irregular verbs must be processed differently.
Historical linguists rarely use the category irregular verb. Since most irregularities can be explained historically, these verbs are only irregular when viewed synchronically, not when seen in their historical context.
When languages are being compared informally, one of the few quantitative statistics which are sometimes cited is the number of irregular verbs. These counts are not particularly accurate for a wide variety of reasons, and academic linguists are reluctant to cite them. But it does seem that some languages have a greater tolerance for paradigm irregularity than others.
