Fork is singular, for example: Tuning fork. “The fork on my bike is blue.” Saying, “the forks on my bike are blue” is sloppy English. Forks I guess is the collective form.
Sheldon “linguist” Brown writes in his dictionary:
Fork
Usually refers to the front fork, the part of the frame set that holds the front wheel. The fork is attached to the main frame by the headset. The fork consists of the two blades that go down to hold the axle, the fork crown, and the steerer.
The term "rear fork" is sometimes used to refer to the part of the frame that holds the rear wheel.
Class dismissed, have a great weekend!
Gordon p