Trittyes were population divisions in ancient Attica

Attica

Attica is a historical region of Greece, containing Athens, the current capital of Greece. The historical region is centered on the Attic peninsula, which projects into the Aegean Sea...

, established by the reforms of Cleisthenes

Cleisthenes

Cleisthenes was a noble Athenian of the Alcmaeonid family. He is credited with reforming the constitution of ancient Athens and setting it on a democratic footing in 508/7 BC...

 in 508 BC. The name means "thirtieth," and there were in fact thirty trittyes in Attica. Each tribe, or phyle

Phyle

Phyle is an ancient Greek term for clan or tribe. They were usually ruled by a basileus...

of Athens

Athens

Athens , is the capital and largest city of Greece. Athens dominates the Attica region and is one of the world's oldest cities, as its recorded history spans around 3,400 years. Classical Athens was a powerful city-state...

 was composed of three trittyes, one from the coast, one from the city, and one from the inland area. Trittyes were composed of one or more deme

Deme

In Ancient Greece, a deme or demos was a subdivision of Attica, the region of Greece surrounding Athens. Demes as simple subdivisions of land in the countryside seem to have existed in the 6th century BC and earlier, but did not acquire particular significance until the reforms of Cleisthenes in...

s; demes were the basic unit of division in Attica.

Further reading

• Traill, John S., The political organization of Attica: a study of the demes, trittyes, and phylai, and their representation in the Athenian Council, Princeton : American School of Classical Studies at Athens
  American School of Classical Studies at Athens
  The American School of Classical Studies at Athens is one of 17 foreign archaeological institutes in Athens, Greece.-General information:...
  
  (ASCSA), 1975