A partial stud nailed next to full studs to support the header at door (and some window) openings.
Framing members, generally 2" x 4"s, which form the inside of the window or door rough opening. They run from the sole plate to the header, which is supported by them.
Short stud, which does not reach from the floor to the ceiling, but only from the floor to a window, for example.
Framing Stud or Bucks. Framing members, generally 2" x 10"s, which form the inside of the window rough opening. They run from the sill to the header, which is supported by them.
A partial stud nailed next to full studs to support the header at door openings. Also called a trimmer.
Vertical framing members, generally 2x4’s, which form the inside of the window or door rough opening. They support the header and run down to the sole plate.