Arabic
In Arabic, defective verbs are called أفعال جامدة (lit., solid verbs). These verbs do not change tense, nor do they form related nouns. A famous example is the verb ليس laysa, which translates as it is not, although it is not the only sister of Kaana which exhibits this property: some Arabic grammaticians argue that دام "daama" (when one of the sisters) is also completely defective; those who refute this claim still consider it partially defective. Some other partially defective verbs are "fati'a" and "zaala," which have neither an imperative form nor an infinitive form when sisters of Kaana.
Read more about this topic: Defective Verb