Learn French: Il n'y a pas d'île dans le lac. - There is no island in the lake.

In French, when you say "there is no [something]", the indefinite articles un and une change to de. Because île starts with a vowel, de drops its 'e' and becomes d'. If this sentence were positive, it would be Il y a une île (There is an island).

How exactly does Il y a become Il n'y a pas?

To make a verb negative in French, you put ne before it and pas after it. In Il y a (there is), the core verb is a and the pronoun y is attached to it. The ne goes before the y and shrinks to n' because y acts like a vowel here. The pas goes right after the verb a.

Does Il n'y a pas mean "there is no" or "there are no"?

It can mean both! The phrase Il n'y a pas de translates to "there is no" or "there are no" depending on the noun that follows it. Here, île is singular, so it means "there is no island". If you wanted to say "there are no islands", you would write Il n'y a pas d'îles—the first part of the sentence stays exactly the same.

Why use dans for "in" instead of another word like en?