A mainly tropical and woody family in which, in common with the previous family and the next one, the pod is the principal kind of fruit.

The family is relatively small in West Africa, its members being recognised by their bipinnate stipulate foliage with, in approximately half of the genera, one or more glands on the leaf rachis of petiole. The leaves often fold down if touched (Fleurat-Lessard, 1985) a response provoked by grazing herbivores, and likely to limit their predation. In so far as the existence of glands encourages the presence of an ant guard, these could also be construed as defensive. The leaflets are conduplicate in the bud.

The inflorescences are spikes or heads, brush like, and made up of small five-part actinomorphic flowers with prominent stamens. The pods, which follow, tend to hang in bunches.

Prickles and/or spines occur in a number of genera. Various Acacia spp. may possess stipular spines or prickles, and pseudo-galls may also be present. Dichrostachys has branch spines. The introduced weeds Schrankia leptocarpa (with four-angled stems, small balls of pink flowers and unjointed four-ridged pods) and Mimosa pudica (with terete stems, mauve flowers and flat-jointed pods) are prickly herbs. The indigenous M. pigra (also in Gambia) is a prickly riverside shrub forming tangles. Young shoots of the forest-emergent Cylicodiscus gabunensis and the swamp and riverain forest trees Cathormion spp. are also prickly.