The term used to describe weak, splitting or brittle nails is Onychoschizia. The common reasons behind this condition are nutritional deficiencies, lack of biotin in diet and lack of moisture/too much moisture in the nails. The best way to prevent brittle nails is to keep them protected by wearing gloves, taking nutritional supplements containing biotin and iron, and by keeping them away from harsh chemicals like detergents and nail polish removers.