A more thorough explanation:

Definition: (adjective, adverb) essential; required; needed. It can also mean convenient, useful, or making good sense.

1. Essential: Water is necessary for survival.

2. Required: It is necessary to wear a helmet while riding a bike.

3. Convenient: It is necessary to have a car if you live in a rural area.

4. Useful: It is necessary to have a good education to get a good job.

5. Making good sense: It is necessary to save money for emergencies.

These examples illustrate how necessary can be used to describe something that is essential, required, convenient, useful, or makes good sense. In each example, the word necessary is used to emphasize the importance of the action or item being described.