- Saccate
- Sagittate
- Saprophyte
- Scaberulous
- Scabrid
- Scale
- Scalpelliform
- Scandent
- Scarious
- Scutellum
- Secondary axis
- Secondary nerves
- Sectile
- Section
- Secund
- Seed
- Semiterete
- Sepal
- Sepals
- Septate
- Septum
- Sericeous
- Serrate
- Serrulate
- Sessile
- Seta
- Setose
- Sigmoid
- Simple
- Sinuate
- Sister group
- Sister groups
- Smooth
- Spatha
- Spatulate
- Spike
- Spur
- Spurred
- Stamen
- Staminode
- Stelidia
- Stellate
- Sterile bracts
- Stigma
- Stigmatophore
- Stipe
- Strigose
- Style
- Sub-
- Subfamily
- Subgenus
- Subterete
- Subtribe
- Subulate
- Succulent
- Sulcate
- Superposed
- Suture
- Symbiont
- Symbiotic
- Sympatric
- Symplesiomorphic
- Symplesiomorphy
- Sympodial
- Synanthous
- Synapomorphic
- Synapomorphy
- Synsepalum
- Syntype
- Systematics