General definitions

Part 1 is the FAA's dictionary. When any other rule in Title 14 uses a defined term, § 1.1 controls what that word legally means — so a disagreement about a regulation often comes down to a definition here.

A few that pilots lean on constantly:

• Aircraft — any device used or intended for flight in the air. Airplane narrows that to an engine-driven, fixed-wing, heavier-than-air craft supported by the dynamic reaction of air against its wings.
• Category and class mean *different* things depending on context. For airman certificates: *category* is a broad group (airplane, rotorcraft, glider, lighter-than-air) and *class* is a sub-group with similar handling (single-engine land, multiengine sea, etc.). For aircraft certification, *category* instead means an airworthiness grouping (normal, utility, acrobatic, transport, restricted…).
• Calibrated airspeed — indicated airspeed corrected for position and instrument error; it equals true airspeed in a standard atmosphere at sea level.
• Ceiling — height above the surface of the lowest broken, overcast, or obscuration layer.
• Controlled airspace — defined airspace where ATC service is provided; a generic umbrella for Classes A, B, C, D, and E.
• PIC, flight time, night, Administrator, approved and dozens more all live here too.

Because the same word can carry a different meaning for *airmen* versus *aircraft*, always read a defined term in the context of the rule citing it.

Summary: Part 1 is Title 14's master glossary; § 1.1 fixes the legal meaning of terms used throughout the FARs (e.g. aircraft, airplane, category, class, calibrated airspeed, ceiling, controlled airspace), and category/class differ for airmen vs. aircraft.