Learn French: L'idée n'est pas importante. - The idea is not important.

In French, when the negative word ne comes right before a verb that starts with a vowel (like est), the e is dropped and replaced with an apostrophe. This is called elision, and it makes the words flow together smoothly.

Where exactly do the negative words go in this sentence?

To make a sentence negative in French, you put the conjugated verb inside a "sandwich" made of ne (or n') and pas. In this sentence, the verb est (is) is sandwiched to make n'est pas (is not).

Why does importante end with an -e?

In French, adjectives have to match the gender of the noun they describe. Idée (idea) is a feminine noun, so the adjective must be in its feminine form. We add an -e to the default masculine word important to get importante.

Since the sentence uses L' instead of La, how can I tell that idée is feminine?