1. A grammatical form of the indefinite article (a, an in English) used to refer to a non-specific or unidentified noun
In English, 'a' and 'an' are the indefinite article forms used before singular nouns
Em inglês, 'a' e 'an' são as formas do artigo indefinido usadas antes de substantivos singulares
2. The variant forms of indefinite articles in different languages, including their variations by gender and number
The indefinite article form 'un' in Spanish changes to 'una' depending on the gender of the noun
A forma do artigo indefinido 'um' em português muda para 'uma' dependendo do gênero do substantivo