Definition
As used with respect to the certification of aircraft, a grouping of aircraft based upon intended use or operating limitations. Examples include transport, normal, utility, acrobatic, limited, restricted, and provisional. As used with respect to the certification of airmen, a broad classification of aircraft based on type — for example, airplane, rotorcraft, glider, and lighter-than-air.
Plain English
In aviation, the word 'category' has two distinct uses. When talking about an aircraft, it describes the type of operation the aircraft was built and certified for. When talking about a pilot's certificate, it describes the broad family of aircraft a pilot is qualified to fly, such as airplane or rotorcraft.
Context Anchor
You will see category on pilot certificates, ratings, aircraft documents, regulations, and FAA explanations of what a pilot or aircraft is approved to do.
Derivation
From the Greek 'kategoria,' meaning a class or group. In aviation, it carries that same idea of sorting things into broad groups — but the FAA uses it in two specific, separate ways depending on whether you are talking about the aircraft or the pilot.
Why Pilots Care
Determines the visibility and ceiling a pilot must have to legally continue an instrument approach to landing.
Intuition Check
Do not read category as just a casual label. In FAA use, it is an official grouping that can affect privileges, approvals, and limits.
Example Sentence 1
The aircraft is certificated in the normal category, which limits the maneuvers the pilot may perform.
Example Sentence 2
When an airplane's approach speed pushes it into Category C, the pilot must use the higher minimums listed for that category.