- saddle
- sagittal
- sagittal crest
- saline
- savannah
- scavenger
- school
- scrub
- sediment
- segment
- sericeous
- serology
- serrate
- sessile
- seta
- setule
- sex
- sexual dichromatism
- sexual dimorphism
- sheath
- silt
- sinuate
- sinus
- skeleton
- soil
- somatic
- spatulate
- sperm
- spermaceti
- spheroidal
- spinal blaze
- spine
- spy-hop
- standard length
- steppe
- sternum
- sting
- stipe
- stock
- stomach
- stranding
- styliform
- sub-
- sub-Recent
- subadult
- subarctic
- subgenus
- subhorizontal
- sublittoral
- subspecies
- substrate
- sulcate
- sulcus
- supraorbital processes
- suture
- swamp
- symbiosis
- sympatric
- sympatric species
- symphysis
- synonym
- systematics