Kohl is a soft, wax- and oil-rich black eyeliner, traditionally a powder or stick and now usually a pencil, that is made to be applied to the waterline and smudged, which is why it moves more than a liquid liner.
Also known as: kajal, kohl pencil, kohl eyeliner, surma, khol
Kohl is the oldest eyeliner there is. The modern cosmetic version is a soft pencil or stick built on castor oil, beeswax and carnauba wax with carbon black pigment (CI 77266). That softness is the point: it glides on the waterline and the inner rim, blends into a smoky edge with a finger, and is the gentlest format for mature eyes. It is also why it migrates. Kohl and kajal wear about 4 to 8 hours unless the formula is waterproof, against 8 to 24 hours for a liquid or gel liner (Iba).
Kajal is the Indian name for the same idea, marketed as soft, cooling and made for the waterline, whereas eyeliner is sold for definition on the lid (House of Makeup). Rock 'N' Kohl from Charlotte Tilbury and Satin Kajal from Victoria Beckham are the prestige examples, the latter with chamomile and panthenol in the formula.
The word also names a traditional product that is not a regulated cosmetic. Kohl, kajal, al-kahal, surma, tiro and tozali sold in markets across Africa, the Middle East, Pakistan and India can be mostly lead sulfide; the US Food and Drug Administration reports that lead sometimes accounts for more than half the weight, and one tiro product linked to lead poisoning in an infant was 82.6 percent lead. None of these materials is an approved colour additive in the United States (FDA). In the EU, colourants in eye products must be listed in Annex IV of the Cosmetics Regulation, which excludes lead compounds.
Buy kohl from a brand that publishes an ingredient list, sharpen it before each use on the waterline, and replace a waterline pencil after 3 months.