The phrase "a category which" is correct and usable in written English.
It can be used when you want to specify or describe a particular category within a broader context.
Example: "We need to identify a category which encompasses all types of renewable energy sources."
Alternatives: "a category that" or "a type that".
"How you are treated"—a category which is as much about respect as it is about pay comes third.
He says he can see why they were met with resistance".Your average person on the street is very sceptical of these drugs because they're classified in the A category, which means, as far as the general person on the street is concerned, they're dangerous, as they're the same category as heroin and cocaine".
(a category which most often includes ourselves).
"Leslie was serene in his contempt for fools, a category which in his view included most of humanity".
Provisions were also made for nontenure track "contract lecturers," a category which included all foreign language teachers.
A sport class is a category which groups athletes depending on how much their impairment impacts on performance in their sport, according to the IPC.
At age 12 all worthy males (a category which until 1978 generally did not include black men) become deacons in the Aaronic priesthood.
The United States also exports a lot of services, a category which covers a broad range of things, like legal services or Internet hosting.
I'm aware that he may have appeared in a category which would indicate that there were concerns about his Mr. Biskupic.
There was a 27% increase in the number of adults trafficked for labour exploitation, a category which includes forcing people into theft, shoplifting, drug production and benefit fraud.
The proportion of state spending that is judged to be "planned" (a category which used to denote capital investment but has become fuzzy) has fallen too.
