Maintain (verb)

1. Keep (something) in good condition through regular checking and repairs.
2. Keep (something) at a particular level or standard.
3. Continue to have or hold (a particular state or condition).
4. Support or defend (a claim, theory, or belief).
5. Provide for or support (someone) financially or materially.

Origin:

Late middle english: from old french maintenir, from latin manu tenere "hold in the hand".

Examples:

1. He maintains his car regularly.
2. She maintains her fitness by exercising regularly.
3. The company maintains high standards of customer service.
4. He maintained his innocence throughout the trial.
5. He is trying to maintain a healthy lifestyle.
6. She is maintaining her grades at a high level.