Learn French: Il y a beaucoup d'aéroports internationaux dans le monde. - There are a lot of international airports in the world.

Internationaux is the masculine plural form of the adjective international. In French, most adjectives and nouns ending in -al change to -aux in the plural. Since aéroports (airports) is masculine and plural, the adjective must match it perfectly.

Since "airports" is plural, shouldn't it be beaucoup des aéroports?

No, because of the word beaucoup (a lot). Expressions of quantity like beaucoup, un peu (a little), and trop (too much or too many) are always followed by de (or d' before a vowel), never by the plural des. You can think of it as saying "a lot of" rather than "a lot of the".

Why does internationaux come after aéroports?

In French, most adjectives come right after the noun they describe. Only a specific group of common, short adjectives (often remembered by the acronym BAGS: Beauty, Age, Goodness, and Size) go before the noun. Because "international" doesn't fall into those categories, it follows the standard rule and goes after the noun.

Why is it dans le monde for "in the world"?