(historical) A period between circa 4000 to 3100 BC which saw the emergence of urban life in Mesopotamia and the Sumerian civilization.

(UK, television) A period of time on a Saturday during which football matches may not be broadcast (so as to avoid reduced attendance in person at other football matches that are not being televised).

(chemistry) A tabular chart of the chemical elements according to their atomic numbers so that elements with similar properties are in the same group (column).

A work of art or drama which evokes a particular historical era. / A work which evokes the era in which it was produced, but may not have any other especial features.

(inorganic chemistry) HIO₄ or H₅IO₆, the oxyacids of iodine in which iodine has the highest oxidation number; H₅IO₆ is a white crystalline substance (HIO₄ is not stable), and both are strong oxidizing agents.

the average interval between fertilization and birth of a mammal; ranges from 13 days for the opossum to 626 days for the Indian elephant

(astronomy) Synonym of non-periodic

(astronomy) Having an orbital period of less than 200 years, especially said of comets

(music) The musical period of time following the Renaissance, extending roughly between 1600-1750.

The period of time during which ovulation takes place. / The period of time between ovulations.