The relation R between two sets of referents A and B is reciprocal iff A R B and B R A; i.e. R is symmetric (mutual). The referents are of the same level, or at any rate adjacent levels, of the empathy hierarchy, and prototypically from its top.
It follows from the definition that A and B have equal control in the situation.

A construction - normally a clause - is reciprocal iff it expresses a reciprocal relation by dedicated structural means. Some reciprocal constructions are as follows:

• The two referent sets involved - A and B - constitute the (coordinated) subject; the predicate is plural.
• A is subject, B is in an oblique dependent; the predicate agrees with A.

In both cases, the predicate may contain a formative expressing or marking reciprocity.

A reciprocal construction may be paraphrased by ‘A R B and B R A’, where R is twice the same verb.

Examples: Svan: liq'h-äl 'kiss each other', lis-jäl 'fight each other', limkarar-äl 'compete', libərg-jäl 'wrestle'.