(formal) If a part of a machine reciprocates, it moves backwards
and
forwards.
Some electric razors have reciprocating heads.
reciprocal adjective FORMAL
A reciprocal action or arrangement involves two people or groups
of
people who behave in the same way or agree to help each other
and give
each other advantages.
The two superpowers agreed to a reciprocal reduction of nuclear
weapons.
Many states have passed laws that will allow nationwide reciprocal
banking.
reciprocally adverb FORMAL
reciprocation noun [U] FORMAL
She had loved him almost all her life without reciprocation (=he
did
not have the same feelings for her).
reciprocity noun [U] FORMAL
Reciprocity is behaviour in which two people or groups of people
give
each other help and advantages.
The two countries have signed a new agreement based on reciprocity
in trade.