- soap dispenser
- soft spot
- soldered side
- solid axle
- solid height
- solid wheel
- solidify
- solo time
- sonic detector
- sorting line
- sorting siding
- sleeper
- sleeper nail
- sleeper section
- sleeper station
- sliding block
- sliding distance
- sliding partition
- slim gauge
- slip switch
- slope protection
- slotted wing
- slow ahead
- slow train
- snow fencing
- sod line
- soil layer
- soundings
- south
- southeasterly
- spacer
- spardeck
- special turnout
- special zone
- specialixed land
- specimen ticket
- speed control
- speed detector
- sounding
- sounding pole
- southeast
- southeast wind
- southeaster
- southern latitude
- southwest
- southwesterly
- span
- spanish burton
- spar
- spar buoy
- spare car
- spark arrester
- speed brake
- speed selector
- speed supervision
- spike drawer
- spin
- spiner
- spike
- spike driver
- spike puller
- spiking
- spinnaker
- spinnaker boom
- spiral curve
- spiral dive
- splice joint
- split sleeper
- spot
- spot board
- spray
- spring line
- sprung mass
- spur track
- splice
- split flap
- split tie
- split web
- spoil car
- stability skirt
- stabilization device
- stable
- stackable container
- stall
- stall trang
- stanchion
- stanchion deckfitting
- stand inshore
- standard coach
- standard container
- standard gauge
- standard time
- standing block
- standing rigging
- star chart
- spoiler
- spot goods
- spot speed
- spot train
- spray hood