reciprocate (v.)

• accord
• affiliate
• agree
• ally
• alternate
• amalgamate
• answer
• associate
• band
• bandy
• change
• coact
• coalesce
• collaborate
• collude
• combine
• commute
• compensate
• complement
• concert
• concord
• concur
• confederate
• consolidate
• conspire
• cooperate
• correspond
• counter
• counterchange
• empathize
• equal
• exchange
• federate
• fuse
• harmonize
• interchange
• join
• league
• logroll
• match
• merge
• partner
• permute
• recompense
• repay
• requite
• respond
• retaliate
• retort
• return
• seesaw
• shuttle
• shuttlecock
• swap
• swing
• switch
• sympathize
• teeter
• teeter-totter
• trade
• transpose
• unite
• wigwag
• zigzag