Leaf Terminology

General Leaf Terminology

Simple leaf	an undivided leaf, with a single blade.
Compound leaf	a divided leaf, separated into 2 or more leaflets.
Trifoliate	a plant with 3 leaves, e.g., trilliums (Trillium, Melanthiaceae).
Blade	the flat, usually photosynthetic portion of the leaf.
Petiole	the stem of the leaf.
Midrib or midvein	the main vascular strand of a leaf (leaflet).
Secondary Veins	econdary ascular strands that branch off the midrib.
Stipule	pairs of small leaf-like structures located at the base of a petiole.
Stipulate Leaf	a leaf with stipules.
Exstipulate Leaf	a leaf without stipules.
Adaxial Surface	the upper surface, the surface facing the stem.

Abaxial Surface	the lower surface, the surface facing away from the stem.

Compound Leaf Terminology

Leaflet	one segment of a compound leaf.
Petiolule	the stem of a leaflet.
Rachis	the main axis of a pinnately compound leaf, appearing as an extension of the petiole.
Rachilla	the secondary axis of a compound leaf.
Pinnately Compound	a compound leaf with leaflets arranged opposite each other.
Bipinnate	a twice-pinnately compound leaf, with each leaflet pinnately divided.
Tripinnate	a thrice-pinnately compound leaf, with each series pinnately divided.
Palmately Compound or palmate leaf	a compound leaf with all the leaflets attached at the same point at the end of the petiole.
Unifoliolate	a leaf with a single leaflet and a petiolule distinct from the petiole, formed from the loss of remaining leaflets of a compound leaf, e.g., redbud (Cercis, Fabaceae).
Geminate or bifoliolate	a leaf with 2 leaflets arising from the same point.
Ternately Compound	a compound leaf with leaflets arranged in multiples of 3.
Ternate or trifoliolate	a compound leaf with 3 leaflets, e.g., clover (Trifolium, Fabaceae).
Biternate	a leaf divided into 3 main divisions, each of which is divided into 3 leaflets.