1. The grammatical form of a word that denotes one person, thing, or instance, as opposed to multiple or plural forms
The singular form of 'children' is 'child'
A forma singular de 'crianças' é 'criança'
2. In linguistics, the inflected form of a noun, pronoun, adjective, or verb that indicates one entity
In English, 'he' is the singular form and 'they' is the plural form
Em português, 'ele' é a forma singular e 'eles' é a forma plural