The term 'kind of fatty acid' refers to two specific types of fatty acids: stearic acid (7 letters) and oleic acid (5 letters). Stearic acid is a saturated fatty acid found in animal fats and vegetable oils, while oleic acid is an unsaturated fatty acid found in olive oil and other plant-based oils. Both fatty acids are important components of the human diet and are essential for maintaining healthy skin and hair.