Null morpheme

In most languages, it is the affixes that are realized as null morphemes, indicating that the derived form does not differ from the stem. For example, plural form sheep can be analyzed as combination of sheep with added null affix for the plural. The process of adding a null affix is called null affixation, null derivation or zero derivation. The concept was first used by the 4th century BCE Sanskrit grammarian from ancient India, Pāṇini, in his Sanskrit grammar.

In English

Inflection

The existence of a null morpheme in a word can also be theorized by contrast with other forms of the same word showing alternative morphemes. For example, the singular number of English nouns is shown by a null morpheme that contrasts with the plural morpheme -s.

• cat = cat + -∅ = ROOT ("cat") + SINGULAR
• cats = cat + -s = ROOT ("cat") + PLURAL

In addition, there are some cases in English where a null morpheme indicates plurality in nouns that take on irregular plurals.

• sheep = sheep + -∅ = ROOT ("sheep") + SINGULAR
• sheep = sheep + -∅ = ROOT ("sheep") + PLURAL

Also, a null morpheme marks the present tense of English verbs in all forms but the third person singular:

• (I) run = run + -∅ = ROOT ("run") + PRESENT: Non-3rd-SINGULAR
• (He) runs = run + -s = ROOT ("run") + PRESENT: 3rd-SINGULAR

Derivation

According to some linguists' view, English verbs such as to clean, to slow, to warm are converted from adjectives by a null morpheme – in contrast to verbs such as to widen or to enable which are also converted from adjectives, but using non-null morphemes. Null derivation, also known as conversion if the word class changes, is very common in analytic languages such as English.