The primary difference between diamond stud and diamond solitaire earrings lie in the design focus. Stud earrings are defined by their form—small, compact earrings that sit on the earlobe, which can feature any material or design. Solitaire earrings, on the other hand, are specifically designed around a single gemstone or diamond, regardless of the earring's overall style (which often, but not exclusively, is in the form of studs).
While stud earrings can be made of various materials (including gemstones, diamonds, pearls, metal, etc.), solitaire earrings specifically highlight a single gemstone or diamond as the centerpiece of the design.
While all solitaire earrings can be considered studs (if they adhere to the stud format), not all stud earrings are solitaires. The term "stud" refers to the earring style, whereas "solitaire" refers to the specific composition featuring a single gemstone or diamond.