Keratosis (from kerat- + -osis) is a growth of keratin on the skin or on mucous membranes stemming from keratinocytes, the prominent cell type in the epidermis. More specifically, it can refer to:

actinic keratosis (also known as solar keratosis)
chronic scar keratosis
hydrocarbon keratosis
keratosis pilaris (KP, also known as follicular keratosis)
seborrheic keratosisActinic keratoses are pre-malignant growths. Seborrheic keratoses are not pre-malignant.