In flight systems, what does the initialism "TCAS" stand for?

The story behind the answer

TCAS stands for Traffic Collision Avoidance System. It’s an onboard safety system that interrogates nearby aircraft transponders (Mode C/S) to spot conflicting traffic and then issues two levels of guidance: Traffic Advisories (TAs) to alert the crew, and Resolution Advisories (RAs) with specific climb/descend instructions to avoid a collision. Crucially, TCAS works independently of air traffic control and has been mandated on most commercial airliners since the 1990s following several mid-air accidents. The current standard, TCAS II v7.1, improved alerting logic to further reduce risk.

Memory tip: Think “C is for Collision”—TCAS’s core job is to avoid collisions, not to handle communication, configuration, or call-signs, which makes the other options incorrect.