What is the technical term for freckles?

The technical term for freckles is "lentigens." Lentigens, commonly referred to as freckles, are small, flat, pigmented spots that usually appear on areas of the skin that are frequently exposed to sunlight. This pigmentation occurs due to an increase in melanin, which is the pigment responsible for the color of the skin, hair, and eyes. Freckles can be genetic and become more pronounced with sun exposure, particularly in individuals with fair skin.

The other terms listed do not relate to freckles. Acetone is a solvent used in various beauty products and has no connection to skin pigmentation. Callous refers to thickened areas of skin that form in response to friction and pressure, while onyx is a type of gemstone and has no relevance to skin conditions or pigmentation. Therefore, lentigens is indeed the accurate and technical term for what we commonly know as freckles.