Technology glossary

Selective Availability

Selective Availability was a GPS feature that intentionally reduced the accuracy available to civilian users. The United States switched it off in May 2000, producing an immediate improvement in civilian positioning accuracy.

Self-Assembled Contact

An electrical contact that reaches its final shape through controlled physical or chemical interactions rather than being patterned completely in place. At very small scales, capillary attraction or surface forces can align electrodes with fragile materials while reducing fabrication damage.

Self-Assembly

A process in which separate components spontaneously organize into an ordered structure through their local interactions, without each placement being directed externally. It occurs in biological systems and is also used in chemistry, nanotechnology, and materials science.

Self-Custody Wallet

A cryptocurrency wallet in which the user, rather than an exchange or custodian, controls the private keys needed to authorize transactions. This gives the user direct control but also makes loss, theft or exposure of the keys the user's responsibility.

Semaglutide

A GLP-1 receptor agonist used to treat type 2 diabetes and, in some formulations, obesity.

Semi-Automated Offside Technology(SAOT)

A football officiating system that combines player-tracking data, ball sensors or video, and algorithms to identify potential offside situations. It alerts match officials and generates supporting visualizations, while the final decision remains with the referee team.

Semiconductor Fab

A highly specialized facility that manufactures integrated circuits on semiconductor wafers.

Semiconductor Supply Chain

The global network of materials, equipment, fabrication, packaging, testing, and logistics required to produce chips.

Sensitivity and Specificity

Two measures of a diagnostic test's accuracy. Sensitivity is how often it correctly catches real cases; specificity is how often it correctly clears healthy cases.

Sensor Fusion

The combination of measurements from multiple sensors to produce a more accurate, complete, or reliable estimate than any single sensor could provide. It is widely used in navigation, robotics, vehicles, smartphones, and tracking systems.

Sentinel Antibody

A pre-existing antibody used as an indicator of a wider immune condition or likely response. It may act as a marker of immune readiness without directly causing the predicted response or targeting the vaccine antigen.

Serological Profiling

The measurement of many antibodies or other blood-serum markers to build a broad picture of immune history or current immune state. Researchers can compare these profiles across people or time points to identify patterns linked to disease or treatment response.

Severe Security Incident

A cybersecurity incident that seriously affects a digital product's ability to protect the availability, authenticity, integrity or confidentiality of data or functions. The Cyber Resilience Act uses defined impact criteria to distinguish reportable severe incidents from routine security events.

Shallow-Water Model

A simplified fluid model that treats horizontal motion as much larger than vertical motion and is often used to study planetary waves and jets.

Shape-Memory Alloy(SMA)

A metal alloy that can recover a preset shape when heated because its crystal structure undergoes a reversible phase transformation.

Shared Socioeconomic Pathway(SSP)

One of several standardized futures used in climate research. Each pathway describes different social, economic and policy conditions and is paired with an emissions and radiative-forcing trajectory.

Shock Compression

A method that sends a rapidly moving pressure wave through a material to create extreme pressure, temperature, and density for a very short time. Scientists use it to study planetary interiors, fusion targets, and matter under conditions that static devices cannot easily reach.

Side-Scan Sonar

A sonar technique that maps seafloor features by sending sound pulses to both sides of a moving platform.

Signal Authentication

Navigation signal authentication lets a receiver verify that received data or ranging signals originate from an authorized source rather than a counterfeit transmitter, helping mitigate some spoofing attacks.

Silicon Spin Qubit

A quantum bit that stores information in the spin state of an electron confined within a silicon device. It can potentially use semiconductor manufacturing methods, but scaling still requires precise control, cryogenic operation and error correction.

SIM AT Interface

A path through which a SIM requests that a device's cellular modem execute AT commands, potentially exposing modem configuration or control functions if the device does not restrict the commands safely.

Single Reporting Platform(SRP)

A central electronic portal that accepts one cybersecurity notification and routes it to the appropriate authorities. ENISA operates the EU platform used for mandatory Cyber Resilience Act reports.

Single-Cell RNA Sequencing(scRNA-seq)

A technique that measures gene activity in individual cells rather than averaging signals across a mixed tissue sample. It helps researchers identify cell types, developmental states and rare cellular responses.

Single-Rotor Drone

An unmanned aircraft that generates most of its lift with one large main rotor, typically using a tail rotor or another mechanism to counter torque. Its helicopter-like design can support efficient hovering and heavier payloads but involves more mechanical complexity than many multirotors.

Skeletal Editing

A chemical strategy that changes atoms within a molecule's core framework without rebuilding the whole molecule.

Skin Microbiome

The community of bacteria, fungi and other microorganisms living on the skin and interacting with its oils, sweat and immune system.

Skin-Electrode Interface

The contact region through which an electrode records electrical signals from the body or delivers electrical stimulation. Its impedance and stability are influenced by skin preparation, moisture, pressure, motion, electrode material, and the use of conductive gels or adhesives.

Sleep Efficiency

The percentage of time spent asleep while in bed.

Sleep Pressure

The homeostatic drive to sleep that generally builds during wakefulness and declines during sleep. It interacts with circadian timing, so tiredness depends on both time awake and the body's internal clock.

Sleep Staging

The process of identifying stages such as light sleep, deep sleep, and rapid eye movement sleep from physiological signals.