improveHis health has improved dramatically since he started exercising.
rallyThe team played badly in the first half but rallied in the second.
recoverWe are still waiting for the economy to recover.
look upinformalOur financial situation is looking up.
pick upinformalBusiness is really beginning to pick up.
work onYou need to work on your technique.
refineA team of experts spent several months refining the software.
by/in leaps and boundsThe sport's popularity has grown by leaps and bounds in the past decade.