Plants perennial (very rarely annual). Inflorescences usually eglandular, occasionally viscid and glandular. Petals equaling sepals. Capsules 9-13 mm. Seeds 0.4-0.9 mm; tubercles small. 2n = ca. 122-152, usually 144. Flowering throughout growing season. A common weed in grassy places: lawns, roadsides, pastures, open woodlands, wastelands; 0-3000 m; introduced; Greenland; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Europe; introduced worldwide. Small annual forms of subsp. vulgare can be difficult to separate from Cerastium pumilum. The latter has smaller capsules, narrower and sharply acute sepals, and short, glandular hairs on the sepals, bracts, and inflorescence.