My apologies if I get a bit technical and preachy. By definition, a nail is a hard, curved plate on the fingers and toes composed of keratin.
Keratin is a tough protein that is also the main constituent of skin and hair.
But just because nails are hard does NOT mean that they are tough and do not require a lot of tender loving care. Dry nails are the most common of all nail conditions. Dryness leads to breakage at the quick, peeling, and low breaks along the side of the nails. Clues to dryness can be seen when the nails are buffed. Light buffing that results in a lot of powder on the buffer is a clear indication of dry nails.