He is devoting himself to his work.

I did my best for the exam.

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.

He overcame the obstacles and achieved his goal.

He has difficulty eating due to dysphagia.

He has a learning disability, but it does not diminish his desire to learn.

We must respect the rights of people with disabilities.