Singular refers to a word form that has one and only one referent, meaning it refers to one person, place, thing, or instance.
Singular is usually contrasted with plural, but in some languages also contrasts with dual (two) and sometimes trial (three).
For example: In English ‘I’ is the 1st person singular form of ‘to be’. ‘We’ is the plural form. In English we only contrast between singular and plural, but other languages (in particular Australian Indigenous languages) may also contrast between ‘we two’, ‘we three’, ‘we but not you’ and more.
The singular form may be indicated on a noun, verb, adjective or other part of speech, or sometimes left unmarked, with the non-singular forms showing the contrast.