Sustenance
Part of speech: noun
Definition: Something that provides support or nourishment.
Example sentence: As our bodies live upon the earth and find sustenance in the fruits which it produces, so our minds feed on the same truths as the intelligible and immutable substance of the divine Word contains.
Keep
Part of speech: noun
Definition: Care, notice.The main tower of a castle or fortress, located within the castle walls.The food or money required to keep someone alive and healthy; one's support, maintenance.
Part of speech: verb
Definition: To maintain possession of.To maintain the condition of.To remain in, to be confined to.To wait for, keep watch for.To restrain.To continue.To remain edible or otherwise usable.To remain in a state.To act as wicket-keeper.to raise; to care for.
Example sentence: Anyone who stops learning is old, whether at twenty or eighty. Anyone who keeps learning stays young. The greatest thing in life is to keep your mind young.