Origin: 1275–1325; ME
incresen, encresen < AF
encres-, MF
encreiss-, s. of
encreistre < L
incrēscere, equiv. to
in- in- 2 +
crēscere to grow;
see crescent 
Related forms: in⋅creas⋅a⋅ble, adjective
Synonyms:
1. expand, extend, prolong. Increase, augment, enlarge may all mean to make larger. To increase means to make greater, as in quantity, extent, degree: to increase someone's salary; to increase the velocity; to increase the (degree of) concentration. Enlarge means to make greater in size, extent, or range: to enlarge a building, a business, one's conceptions. Augment, a more formal word, means to make greater, esp. by addition from the outside: to augment one's income (by doing extra work). 3. expand, grow, develop, swell. 6. enlargement, expansion.
Antonyms:
1, 3. decrease.