Circles, radii, diameter.

They measured something.

Actually, not neccessary. Simple measurements, squares would do the same thing, hanging strings and straight lines.

LENGTH: DAKTYLOS–referred to a finger segment

1 DAKTULOS (plural–“Daktyloi”) = 2 cm

1 POUS (Foot in English)=16 DAKTYLOI

1 PECHUS = 24 DAKTYLOI

1 PLETHRON =100 PODES (plural of Pous) =4 English acres

1 STADION/STADIA = 600 PODES

Dry Measure

1 medimnos (m) = 48 choenices (m.pl. of choenix) =approximately 25kg of grain)

1 choenix (m.) = 4 kotylae (pl. of kotyle)

1 kotyle (f.) = 6 kyathoi (m.;pl. of kyathos)

Liquid Measure

1 metretes (m.) = 12 choes (m.;pl. of chous)

(approximately 34L)

1 chous (m.) = 12 kotylai

1 kotyle (f.) = 6 kyathoi

Currency

The basic unit of Athenian currency was the obol:

OBOL:

After 449 BC, 1 drachma (f.) = 6 obols (m.) pl. of obol)

1 stater (m.) = 2 drachmae (f.;pl. of drachma)

1 mina (f.) = 100 drachmae

1 talent (n.) = 60 minae (f.; pl. of mina)

Weight

Athenian weights were associated with currency since units of currency involved prescribed amounts of a given metal.

1 obol (m.)= approximately 0.7 grams

1 drachma (f.) = 6 obols (m.; pl. of obol)

1 stater (m.) = 2 drachmae (f. ; pl. of drachma)

1 mina (f.) = 100 drachmae (f.ρ;pl. of drachma)

1 talent (n.) = 60 minae (f. ; pl. of mina)(approximately 26kg)

Time

Athenians measured the day by sundials. Periods during night or day could be measured by a water ‘clock’ that dripped at a steady rate. The year was divided into 12 months, with one month being repeated every second year. Even with this intercalary month, the Athenian or Attic calendar was still fairly inaccurate and days had occasionally to be added by the Archon Basileus. The months were named after Athenian religious festivals (the actual order of the months in the Athenian Calendar, and their corresponding months of our contemporary Gregorian calendar:

Gamelion (7th Dec-Jan)

Anthesterion (8th: Jan-Feb)

Elaphebolion (9th: Feb-March)

Mοunichion (10th: March-April)

Thargelion (11th: April-May)

Skirophorion (12th: May-June)

Hekatombaeon (1st: June-July)

Metageitnion (2nd: July-Aug)

Boedromion (3rd: Aug-Sept)

Pyanepsion (4th: Sept-Oct)

Maimakterion (5th: Oct-Nov)

Poseideon (6th: Nov-Dec)

For information dating back even further, see the excellent article at http://en.wikipedia.org/wiki/History_of_measurements.