Trees, evergreen or semievergreen, rarely deciduous in dry season. Xylem with aromatic resin in intercellular resin canals. Branchlets with stipular scars, sometimes annular. Leaves simple, alternate; stipules persistent or caducous, large or small; leaf blade with lateral veins pinnate, margin entire or sinuate-crenate. Inflorescences few- or many-flowered, terminal or axillary racemes or panicles; flowers usually sweetly scented; bracts usually fugacious and minute, rarely persistent and large. Inflorescences, calyces, petals, ovary, and other parts usually with stellate, squamate, fascicled or free-standing hairs. Flowers bisexual, actinomorphic, contorted. Calyx lobes 5, free or united at base, imbricate in bud if not united. Petals 5, adnate or connate at base. Stamens (10-)15 to many, free from or connate to petals; filaments usually dilated at base; anthers 2-celled, with 2 pollen sacs per cell (Chinese species); connective appendages aristate, filiform or stout. Ovary superior, rarely semi-inferior, slightly immersed in torus, usually 3-loculed, each locule 2-, rarely many ovuled; ovules pendulous, lateral or anatropous. Fruit usually nutlike, sometimes capsular and 3-valved, 1(to many)-seeded, with persistent, variously accrescent calyx of which 2 or more lobes are usually developed into lorate wings. Seed exalbuminous; cotyledons fleshy, equal or unequal, applanate or ± folded or cerebriform, entire or laciniate; radicle directed toward hilum, usually included between cotyledons.
Leaves alternate, entire, penninerved; indumentum often of two kinds, of stellate hairs or rarely of peltáte scales; stipules mostly small and deciduous, sometimes very large and enclosing the young bud, rarely persistent, leaving an annular scar after falling away
Flowers hermaphrodite, actinomorphic, fragrant, in axillary panicles
Calyx-tube short or well developed, free or adnate to the ovary; lobes 5, imbricate or valvate, mostly greatly enlarged, wing-like, and ascending in fruit and then strongly nervose, rarely small and reflexed or spreading
Seeds without endosperm; cotyledons thick and equal or variously contorted
Fruit free from or included in the enlarged calyx-tube, rarely closely adnate to it, indehiscent, usually 1-seeded
Ovary inserted on the broad torus or slightly immersed in it, 3-celled; style subulate or variously thickened, entire or 3-lobed; ovules 2 in each cell
Stamens rarely definite, hypogynous or subperigynous; filaments short, often dilated at the base; anthers 2-celled, opening lengthwise; connective mucronate or aristate or club-shaped