To make less; to reduce; to make smaller, or fewer; to diminish; to lower; to degrade; as, to lessen a kingdom, or a population; to lessen speed, rank, fortune.

To become less; to shrink; to contract; to decrease; to be diminished; as, the apparent magnitude of objects lessens as we recede from them; his care, or his wealth, lessened.

decrease in size, extent, or range; "The amount of homework decreased towards the end of the semester"; "The cabin pressure fell dramatically"; "her weight fall to under a hundred pounds"; "his voice fell to a whisper"

make smaller; "He decreased his staff"