A large family, widely distributed, most abundant in the northern hemisphere, including both the handsome Pinks and the insignificant Chickweeds. They are herbs, with regular, mostly perfect flowers, with four or five sepals; usually with four or five petals, sometimes with none; stamens as many, or twice as many, as the petals; ovary superior, one-celled; styles two to five in number; fruit a capsule, containing several or many, kidney-shaped seeds, opening by valves, or by teeth, at the top; leaves opposite, toothless; stems usually swollen at the joints. The name Pink comes from the petals of some kinds being cut into points, or "pinked."

There are numerous kinds of Arenaria, widely distributed, difficult to distinguish, with small, white flowers with five petals, usually not notched, ten stamens and usually three styles; leaves usually long and narrow, often stiff and growing in tufts; capsule roundish, splitting into usually three valves, each with two parts. These plants often grow in dry, sandy places, some at very high altitudes, some by the sea, hence the Latin name meaning "sandy," and the common one, Sandwort.