His phone rang while he was in the middle of a meal.

Essential amino acids are necessary to be taken from our diet because our body cannot produce them on its own.

Essential amino acids cannot be produced in the body, so they need to be obtained from the diet.

Do you understand the necessity of this project?

That information is unnecessary.

That information is completely unnecessary.

He thinks that war is a necessary evil.

The disadvantage of his plan is that it takes too much time.

There is a serious lack in that contract.

His body is very healthy.