| Name | Structure/ Category | Description |
|---|---|---|
| Odd-pinnate | [Terminal leaflet] {presence} | Pinnately compound with an odd number of leaflets, one of them terminal. |
| Once palmately compound | [Leaves] {complexity form} | Compound with leaflets all attached at a common point and diverging from one another. |
| Once pinnately compound | [Leaves] {complexity form} | Compound with leaflets attached at different points along and on either side of a central axis or rachis. |
| Once pinnately lobed | [Leaves] {lobing form} | With several main segments or lobes positioned along and on either side of a central axis; lobed in a feather-like pattern. |
| Once pinnate-pinnatifid | [Leaves] {complexity form} | Once pinnately compound with pinnatifid leaflets. |
| Opposite | [Leaves] {insertion} | Positioned in pairs along the stem, the members of each pair at the same level across from one another; two leaves occurring at each node. |
| Orbiculate | [Leaflets, Leaves, Petals, Phyllaries, Sepals] {shape} | Approximately circular in outline. |
| Oval | (1) [Leaflets, Leaves, Petals, Phyllaries, Sepals] {shape} | Broadly elliptic, the width more than one-half the length, with rounded ends. |
| Oval | (2) [Leaf cross section] {shape} | Elliptic in cross section. |
| Ovary | [Flowers] | The lower portion of a pistil where ovules are borne; often distinguishable from the rest of the pistil by its larger circumference. |
