Learn Spanish (Spain): Los niños enfermos necesitan una pastilla.

In Spanish, describing words (adjectives) usually come after the noun they describe. So instead of saying 'sick children', you say 'children sick' (niños enfermos).

Why does enfermos end in an 's'?

Adjectives must match the noun they describe in both gender (masculine or feminine) and number (singular or plural). Since niños is a plural noun, the adjective enfermos must also be plural, which is why it adds an 's'.

Does niños mean 'boys' or 'children'?

It can mean both! In Spanish, the masculine plural niños is used to refer to a group of just boys, or a mixed group of boys and girls. Context usually tells you which one it is, and here 'children' is the most natural fit.

Why does the verb necesitan end in '-an'?

Necesitan is the 'they' form of the verb necesitar (to need). Because the subject doing the needing is los niños (a third-person plural group, or 'they'), you drop the '-ar' ending and add '-an' for the present tense.