Thou1, pron.
[nom. THOU; poss. THY, or THINE; obj. THEE; pl. nom. YOU; poss. YOUR, or YOURS; obj. YOU.] [A-S. thū, thu, O. Sax. & Icel. thū, Goth. thu, O. H. Ger. dū, N. H. Ger., Sw., & Dan. du, allied to Lat. tu, Gr. σύ, Dor. τώ, Slav. ty, Celt. ti, Skr. tvam.] The second personal pronoun, in the singular number, denoting the person addressed; thyself; the pronoun which is used in addressing persons in the solemn or poetical style.
Art thou he that should come? Matt. xi. 3.
Thou was in former times customarily used in very familiar language. It is also now sometimes used by the Friends, or Quakers, though the most of them corruptly say thee instead of thou.