The Three Constituents of the World (San Seken) are:

• Shujō Seken – World of sentient beings; living beings such as human and animals.
• Go-on Seken – World of the five elemental aggregates which form body, mind and environment.
• Kokudo Seken – World of non sentient beings; the land where living beings live.

Each of the constituents has the ten suchnesses, so one thousand suchnesses multiplied by the Three Constituents equal 3,000 realms.