TSI

TSI may refer to:

Science, technology and engineering

• Thyroid Stimulating Immunoglobulin
• Time-Slot Interchange, a technique used to switch networks
• Total Solar Irradiance, the total energy output of the sun
• Trophic state index
• TSI, Triple Sugar Iron test, TSI slant, a microbiological test for enteric bacteria such as Salmonella and Shigella
• TSI, Turbine Supervisory Instrumentation, sensors and monitors dedicated for measurement of mechanical parameters like vibration, elongation, expansion in steam/gas/water turbines. Sometimes also rotational speed and temperatures.

Motor vehicle technologies

• TSI, an acronym used by Volkswagen Group for petrol engines featuring its "twincharger" (turbocharger plus supercharger) and Fuel Stratified Injection technologies; latterly, also used for engines featuring only a turbocharger and Fuel Stratified Injection

Standards, and standards organisations

• Trading Standards Institute, a British professional association
• TSI, Technical Specifications for Interoperability for the European railway system

Companies

• TeleSensory, Inc., a maker of speech products and products intended for the blind
• TSI Inc, an aerosol instrument company headquartered in St. Paul, MN
• Town Sports International, an operator of fitness facilities
• TekSavvy Solutions Inc., a Canadian residential and business telecommunications company
• TSI (Trict Scooters International), an American freestyle scooter designer/ creator

Organisations

• The Security Institute (SyI), a United Kingdom based professional body for security professionals
• The Seasteading Institute

Media, and entertainment

• Televisione svizzera di lingua italiana, Swiss television in the Italian language
• "The Spaghetti Incident?", a 1993 covers album by Guns N' Roses

People and places

• Torres Strait Islanders, an Australian indigenous people
• Torres Strait Islands, a group of at least 274 small islands

Other

• True Strength Index, an indicator used in technical analysis of financial markets.
• Tissue Saturation Index, an absolute indicator of oxygenated hemoglobin, which is measured (regionally and non-invasively) by NIRS. TSI is also referred to as $StO_2 \,$.