Learn Hardcore Spanish (Latin America): Los niños corren en el patio.

Los is the plural definite article for masculine nouns in Spanish. Since niños (which means boys or children) is plural, we need to use los rather than el, which is used only for singular masculine nouns.

Why is niños used instead of other words like chicos or muchachos?

All these words can mean boys or children, but niños is the most neutral and common choice. Chicos can sound more casual or regional, and muchachos can imply older children or teenagers in some areas. Niños clearly refers to mixed groups of younger children.

Why does the verb correr change to corren in this sentence?

In Spanish, verbs must agree with their subject in number and person. Corren is the present tense conjugation of correr for the third person plural (they run). Since los niños is they in English, we use corren.

What does en mean in en el patio?

En generally means in or on. In this context, it means in or at the patio. It indicates where the children are running: in the patio area, not somewhere else.

Can we say al patio instead of en el patio?

Not in this context. Al patio implies movement towards the patio (to the patio). Since the children are already running around in the patio, en el patio is correct to indicate location rather than destination.