Editing Defective verb (section)

==Classical Greek==
"No single [[Classical Greek|Greek]] verb shows all the tenses", and "most verbs have only six of" the nine classes of tense-systems, and "[s]carcely any verb shows all nine systems".<ref>{{cite book|last=Smyth|first=Herbert Weir|author-link=Herbert Weir Smyth|title=Greek Grammar|location=Cambridge, Massachusetts|publisher=Harvard University Press|year=1956|orig-year=1920|isbn=0-674-36250-0|pages=108–109}} §§362, 368a</ref>

The verb χρή (''khrē'', 'it is necessary'), only exists in the third-person-singular present and imperfect ἐχρῆν / χρῆν (''ekhrēn / khrēn'', 'it was necessary').

There are also verbs like οἶδα (''oida'', 'I know'), which use the perfect form for the present and the pluperfect (here ᾔδη ''ēidē'', 'I was knowing') for the imperfect.

Additionally, the verb εἰμί (''eimi'', 'I am') only has a present, a future and an imperfect – it lacks an aorist, a perfect, a pluperfect and a future perfect.