THESAURUS
strengthen
accelerate, accrue, accumulate, add to, advance, affirm, aggravate, animate, anneal, appreciate, attest, augment, authenticate, back, back up, balloon, be tough, bear out, beef up, bloat, blow up, bolster, boom, boost, brace, brace up, breed, broaden, buttress, case harden, certify, cheer, chirk up, circumstantiate, complicate, concentrate, condense, confirm, consolidate, corroborate, crescendo, deepen, develop, document, double, embolden, encourage, endure, energize, enhance, exacerbate, exaggerate, fortify, gain, gain strength, gelt, get ahead, gird, go up, grow, hang tough, harden, hearten, heat up, heighten, hop up, hot up, increase, inspirit, intensify, invigorate, jazz up, key up, magnify, make complex, mount, multiply, nerve, nourish, nutrify, prepare, probate, proliferate, prop, prove, ramify, ratify, ready, recruit, redouble, refresh, reinforce, reinvigorate, rejuvenate, renew, restrengthen, rigidify, rise, run up, screw up, sharpen, shoot up, shore up, sinew, snowball, soup up, spread, steel, step up, stiffen, substantiate, supplement, support, sustain, swell, temper, tense, tighten, tone up, toughen, trice up, triple, undergird, uphold, validate, verify, vitalize, warrant, wax, whet, widen
ROGET THESAURUS
strengthen
Increase
VB
increase, augment, add to, enlarge, dilate, grow, wax, get ahead, gain strength, advance, run up, shoot up, rise, ascend, sprout, aggrandize, raise, exalt, deepen, heighten,
strengthen, intensify, enhance, magnify, redouble, aggravate, exaggerate, exasperate, exacerbate, add fuel to the flame, oleum addere camino, superadd, spread.
Power
VB
be powerful, gain power, belong to, pertain to, lie in one's power, be in one's power, can, be able, give power, confer power, exercise power, empower, enable, invest, indue, endue, endow, arm,
strengthen, compel.
Strength
VB
be strong, be stronger, overmatch, render strong, give strength,
strengthen, invigorate, brace, nerve, fortify, sustain, harden, case harden, steel, gird, screw up, wind up, set up, gird up one's loins, brace up one's loins, recruit, set on one's legs, vivify, refresh, refect, reinforce, reenforce.