Article is a determiner to express the gender and the number of the noun.
Article can be:
- Definite article: To express gender and number of a noun known by the the speaker and the writer, to refer something that has already been mentioned. Definite articles in Spanish:
In Spanish language definite articles agree in gender (masculine or feminine) and in number (singular or plural) with the noun that they accompany.
un libro - unos libros,
un profesor - unos profesores
una mesa - unas mesas,
una doctora, unas doctoras
Remark: In Spanish to express the profession with the verb to be, the indifinete article is not used, except when the noun is modified by an adjective. Correct: Soy profesor de español. Incorrect: Soy un profesor de español. Correct: Soy una buena profesora de español.