Trees, shrubs, rarely herbs, often prickly or spinose. Leaves bipinnate; leaflets small and numerous or leaves reduced to phyllodes; petiolar glands often present; stipules generally spinescent. Inflorescence cylindric spike or globose head; peduncle solitary axillary or fasciculate or paniculate at the end of branches; bracts often two, scale like, situated on the peduncle at various levels. Flowers small, 3-5-merous, bisexual or plants polygamous. Calyx campanulate, dentate, lobed or polysepalous. Petals usually more or less united, rarely absent. Stamens indefinite, free or shortly and irregularly connate at the base; anthers small, eglandular. Ovary sessile or stipitate, with 2 or more ovules. Fruit ovate to linear, straight, arcuate or contorted, membranous to woody, rarely articulated or moniliform. Seed large, with a filiform funicle or fleshy aril.