Maintain v. t. : To hold or keep in any particular state or condition; to support; to sustain; to uphold; to keep up; not to suffer to fail or decline; as, to maintain a certain degree of heat in a furnace; to maintain a fence or a railroad; to maintain the digestive process or powers of the stomach; to maintain the fertility of soil; to maintain present reputation.

Maintain v. t. : To keep possession of; to hold and defend; not to surrender or relinquish.

Maintain v. t. : To continue; not to suffer to cease or fail.

Maintain v. t. : To bear the expense of; to support; to keep up; to supply with what is needed.

Maintain v. t. : To affirm; to support or defend by argument.

Example:
Why is it important to Maintain the genetic diversity of crop plants?

Taxonomy
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maintain from the Merriam-Webster Online Dictionary with audio pronunciations, thesaurus, Word of the Day, and word games.