In morpheme-based morphology, a
null morpheme is a
morpheme that is realized by a
phonologically null
affix (an empty string of phonological segments). In simpler terms, a null morpheme is an "invisible" affix. It is also called a
zero morpheme; the process of adding a null morpheme is called
null affixation,
null derivation or
zero derivation. The concept was first used over two thousand years ago by 4th century
Sanskrit grammarian from ancient India,
Pāṇini, in his
Sanskrit grammar. Some linguists object to the notion of a null morpheme, arguing that it sets up an unverifiable distinction between a "null" or "zero" element, and nothing at all.