Section 4: Players & Officials

Each team may have 18 players on the playing surface at any one time, with no more than four interchange players (Law 5.1). Variation of that number is provided for separately (Law 5.2).

Source: Law 5.1, Law 5.2, Law 8, Law 8.1, Law 8.2, Law 6, Law 12, Law 12.1, Law 12.2, Law 10.2

Send this to your friend — argument over.