Also called: Nail ridges · Beau's lines · Brittle nails · Pitted nails · Nail biting

Where on the hand: On the surface of the nail plate and immediately under it.

What it looks like: Fine lines running lengthwise (vertical ridging) or across the nail (horizontal grooves), plus splitting, small surface dents, and dark lines beneath the plate.

Texture is read as constitutional quality and as a record of events. Vertical ridges describe a standing state — delicacy, nervousness, chronic stress. Horizontal grooves describe a discrete event, and because nails grow at a known rate, the distance from the cuticle dates that event.

Read with care: Every reading here is traditional folk-health doctrine. Beau's lines and pitting do have recognised medical causes; the correct response to a worrying nail is a clinician, not a reading.