A braided monoidal category is a monoidal category equipped with natural isomorphisms satisfying the two hexagon
identities. For a strict monoidal category
these identities read
and
In general, the associativity isomorphisms enter these formulas. The braiding is symmetric when (Etingof et al. 2015, pp. 195-197).
Vector spaces over a fixed field
with
give a symmetric example. A braided monoidal
functor preserves the braidings as well as the monoidal structure (Etingof et
al. 2015, p. 196).