Spoon nails, also known as koilonychia, are nails that curve inward and resemble the shape of a spoon. This can be a sign of iron deficiency anemia, hemochromatosis (a condition where your body absorbs too much iron), or malnutrition.
Clubbed nails are nails that curve outward, and the tips of your fingers enlarge. This can be a sign of lung disease, heart disease, or inflammatory bowel disease.
Nail pitting is small indentations in the surface of the nail that look like little craters. This can be a sign of psoriasis, eczema, or alopecia areata (an autoimmune disease that causes hair loss).
Beau's lines are deep indentations that run across the width of the nail. They can appear after a severe illness, injury to the fingernail, or zinc deficiency.
Nail separation is when the nail loosens and separates from the nail bed. This can be caused by a fungal infection, psoriasis, or injury.
Yellow nails syndrome is a rare condition that causes the nails to thicken and turn yellow. It can be a sign of respiratory problems, lymphedema (fluid buildup in the tissues), or psoriasis.
Terry's nails are nails that appear white across most of the nail plate, with a darker pink or red rim at the tip. This can be a sign of liver disease, congestive heart failure, or diabetes.
Brittle nails are nails that crack, split, or break easily. This can be caused by dehydration, aging, nutritional deficiencies, or frequent use of nail polish remover.