The phrase "a subject which was" is correct and usable in written English.
It can be used when referring to a topic or matter that has been previously discussed or is being described in a past context.
Example: "The research paper focused on a subject which was often overlooked in previous studies."
Alternatives: "a topic that was" or "an issue which was".
The second course of lectures was devoted to the principles of Plant Breeding, a subject which was then very new in every part of the United States...
And a win for Apple as well, as it has been proven throughout the years that they don't get social — a subject which was a topic of debate again yesterday coincidentally.
It's a subject which was previously covered in the 1979 play Bent by Martin Sherman (and the play's 1997 movie adaption), as well as the 2000 documentary Paragraph 175.
The last time I attended the class she gently corrected me after I gave a short extemporaneous talk to the class about a subject which was given to me.
Back then, China was only just starting to emerge from its isolation in the international community, and my own interest in studying Chinese raised many eyebrows -- as if I were pursuing a subject which was way out on the fringe, and had little practical career applications.
We also tried to find any correlations between molecular profile and radiological features, a subject which was completely unknown for PAs.
Acceptance of a subject which is not designated for HASS credit (including Harvard and Wellesley subjects).
It is a subject which is absolutely in the ether right now.
"I'm very surprised to see I became a subject, which is very shocking to me," he said.
Picoult has a formula: choose a subject which is soon to become controversial and tell the story through a rotating cast of characters.
But whether she intended to or not she also managed to make a remark about a subject which is sensitive for him - his weight.
