| term | definition | image |
| Acroscopic | Facing apically | |
| Actinodromous | With three or more primary veins diverging radially from a single point at or above the base of the ... | |
| Actinomorphic | Flowers with radial symmetry and parts arranged at one level; with definite numbers of parts and siz... | g-actinomorphic.png |
| Actinostele | A protostele having a xylem core in the form of radiating ribs, as viewed in transverse section | |
| Aculeate | Prickly | g-aculeate.png |
| Acuminate | Gradually tapering to a sharp point, forming concave sides along the tip. (Compare with acute.) | g-acuminate.png |
| Acute | Tapering to a pointed apex with more or less straight sides, the sides coming together at an angle o... | g-acute.png |
| Adaxial | Next to the axis; facing the stem; ventral | g-dorsal-ventral.png |
| Adherent | With unlike parts of organs joined, but only superficially and without actual histological continuit... | |
| Adnate | With unlike parts or organs integrally fused to one another with histological continuity | |
| Adpressed | Pressed closely to axis upward with angle of divergence 15 degrees or less | |
| Adventitious | Structures or organs arising in a position that is unusual for their type, as roots originating on t... | |
| Adventitious root | Root arising from part of plant other than root; usually produced laterally on aerial stems. | |
| Aerating | Vertical or horizontal aboveground roots. | g-knee.png |
| Aerial | Fibrous, adventitious roots, frequently with an adhesive disk; a crampon. | |
| Aerial roots | Roots that grow above ground and are not covered by soil or water. | |
| Aerial stem | A prostrate to erect, above ground stem. | |
| Aerocaulous | With aerial stems | |
| Aerophyllous | With aerial leaves | |
| Aestival | Appearing in summer | |
| Agamandrous | Inflorescence with neuter flowers inside or above and staminate outside or below (agamandrocephalous... | g-agamandrous.png |
| Agamogynous | Inflorescence with neuter flowers inside or above and pistillate outside or below (agamogynecephalou... | g-agamogynous.png |
| Agamohermaphroditic | Inflorescence with neuter flowers inside or above and hermaphroditic outside or below (agamohermaphr... | g-agamohermaphroditic.png |
| Agamous | Without sex; sexual organs abortive | g-neuter.png |
| Agglomerate | Dense structures with varied angles of divergence | |
| term | definition | image |