- Abaxial
- Abaxially
- Abscission layer
- Acaulescent
- Acrotonic
- Actinomorphic
- Aculeate
- Acuminate
- Acute
- Adaxial
- Adaxially
- Adnate
- Adventitious
- Aerial roots
- Aestivation
- Alate
- Allopatric
- Alternate
- Amplexicaul
- Ancipitous
- Angular
- Anther
- Anthesis
- Antrorse
- Aphyllous
- Apical
- Apiculate
- Apomixis
- Apomorphic
- Apomorphy
- Appressed
- Approximate
- Arachnoid
- Arcuate
- Aristate
- Articulate
- Articulation
- Ascending
- Asexual flowers
- Attenuate
- Auricle
- Auriculate
- Autapomorphic
- Autapomorphy
- Autogamous
- Autotrophic plant
- Axillary