1. A government of five.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• genearchy,
• gunnarchy,
• Krytarchy,
• pentarcon,
• pentalph,
• pentapidy,
• oentarchy,
• lentarchy,
• -entarchy,
• 0entarchy,
• pwntarchy,
• psntarchy,
• pdntarchy,
• prntarchy,
• p4ntarchy,
• p3ntarchy,
• pebtarchy,
• pemtarchy,
• pentatchy,
• Puntarchy

The plural of the "Pentarchy" can be the "pentarchies".

The singular of the "Pentarchy" can be the "Pentarchy".