- siemens
- siemilogarithmic scale
- single sampling
- single selection
- single shift
- single site
- single spacing
- single span
- single station
- single step
- single tasking
- single threading
- single user
- single window
- single-address
- single-click
- single-level
- single-space
- single-stage
- singular
- singular colineation
- singular collineation
- singular conic
- singular correlation
- singular correspondence
- singular determinant
- singular distribution
- singular element
- singular index
- singular integral
- singular line
- Singular matrix
- singular plane
- singular proposition
- singular quadratic
- singular quadric
- singular series
- singular surface
- singular tangent
- singular transformation
- sinistrorsal curve
- sink
- sink block
- sieving process
- sigma
- sigma storage
- sigma-field
- sigma-function
- sigmoid
- sign character
- sign condition
- sign digit
- sign on
- sign test
- sign-post
- signal channel
- signal circuit
- signal comparator
- signal conditioner
- signal contrast
- signal detection
- signal distance
- signal generator
- signal handler
- signal indicator
- signal intensity
- signal name
- signal normalization
- signal processing
- signal saturation
- signal supply
- signal transformation
- signaling current
- signaling rate
- signalling
- signalling function
- signalling link
- signalling message
- signalling network
- signalling protocol
- signed character
- signed decimal
- signed integer
- signed numbers
- significance
- significance test
- significant condition
- significant digit
- signincant instant
- signum function
- similar conics
- similar figures
- similar matrix
- similar polygons
- similar region
- similar solids
- similar triangles
- similarity hypothesis
- similarity transformation
- sinuous