Hospital (Lat. hospitalia, apartments for guests), an institution for the reception and relief of the sick, wounded, or infirm. The word has undergone great changes of signification. The earliest known hospital for the sick was founded in the latter part of the 4th century at Caesarea; St. Chrysostom built one at his own expense in Constantinople ; and Fabi-ola, the friend of St. Jerome, founded one at Rome. The Hotel-Dieu in Paris, founded in the 7th century, has long been the largest and finest hospital in the world. It was rebuilt in the 12th century, and has been extended from time to time until now it covers five acres. The Hotel-Dieu of Lyons, said to have been founded by Childebert in the 6th century, almost equals it. Rome had 2'4 hospitals in the 9th century; and in the 11th they began to be established for pilgrims in the Holy Land. Archbishop Lanfranc built a hospital at Canterbury in 1070. The oldest hospitals in London are St. Bartholomew's, which dates from 1546; Bethlehem, 1547; and St. Thomas's, 1553. In all civilized countries every considerable city now has one or more hospitals, sustained by charity, endowment, or government grants. Frequently they are connected with medical schools, for mutual advantage.

Many have elaborate and costly buildings; but the latest theories are not in favor of permanent structures, which are believed to harbor the germs of disease. Military field hospitals, first known in the 6th century, have now, in connection with the ambulance system (see Ambulance), been made highly efficient. A yellow flag is the sign of a hospital.