diptote
A noun which has only two cases.
In Modern Standard Arabic, nouns belong to triptotes or diptotes, or can be indeclinable.
Where it comes from
From Latin diptōtum, from Ancient Greek δίπτωτος (díptōtos), from δί- (dí-) + πτῶσις (ptôsis, “case”).
Adapted from the Wiktionary entry diptote (CC BY-SA 4.0).