The Ancient Greek word oikos (Ancient Greek: (pronunciation oi•kos<ref
name= oi-note >Note: approximately, and still certainly a diphthong. (For Attic Greek, spelling is still a reliable guide to pronunciation for the ⟨⟩ form.)</ref>); plural: ; English prefix: eco- in (eg) ecology and economics) referred to three related but distinct concepts: the family, the family's property, and the house. Its meaning shifts even within texts.
The oikos was the basic unit of society in most Greek city-states. In normal Attic usage the oikos, in the context of families, referred to a line of descent from father to son from generation to generation.<ref name= MacDowell > </ref> Alternatively, as Aristotle used it in his Politics, the term was sometimes used to refer to everybody living in a given house. Thus, the head of the oikos, along with his immediate family and his slaves, would all be encompassed.<ref name= Cox > </ref> Large oikoi also had farms that were usually tended by the slaves, which were also the basic agricultural unit of the ancient Greek economy.
Layout
Traditional interpretations of the layout of the oikos in Classical Athens have divided into men's and women's spaces, with an area known as the gynaikon or gynaikonitis associated with women's activities such as cooking and textiles work,<ref name= Morris > </ref> and an area restricted to men called the andron.<ref name= Nevett > </ref> In Lysias' speech On the Murder of Eratosthenes, the women's rooms were said to be situated above the men's quarters,<ref name= Lysias > Lysias, I.9, I.33 </ref> while in Xenophon the women's and men's quarters are next to one another.<ref name= Xenophon > Xenophon, Oeconomicos (Oeconomus), ix.5, 7.35–7 </ref>
More recent scholarship from historians such as Lisa Nevett and Lin Foxhall has argued for a more flexible approach to household space, with rooms not simply having a single fixed function,<ref name= Foxhall,2007 > </ref> and gendering of space not being as simple as some rooms being for men and others for women. It has been argued that instead of dividing the household space into "male" and "female" areas, it is more accurate to look at areas as being private or public. In this model, access to the private areas was restricted to the family, while public areas accommodated visitors.
In Olynthos and Halieis, street plans in the classical city were rectilinear, and thus houses were of regular shapes and sizes. By contrast, in Athens houses appear to have varied much more in size and shape. In the classical period, houses excavated from Olynthos were "invariably" organised around a colonnaded courtyard. Likewise, of the houses excavated at Halieis in the Argolid, most of the houses seem to have had a single entrance which gave access to a court, and Nevett also cites three buildings excavated on Thasos as being similarly arranged around a courtyard. Only a minority of the houses had surviving evidence of staircases, demonstrating that they definitely had upper storeys, while for the remainder of Olynthian houses the evidence is inconclusive. On the Murder of Eratosthenes demonstrates that at least some Athenian houses also had an upper storey. Entranceways at Olynthos were designed for privacy, preventing passers-by from seeing inside the house.
Historians have identified a "hearth-room" in ancient Greek houses as a centre of female activity. However, Foxhall has argued that Greek houses often had no permanent kitchens. For example, a house in Attica known as the Vari House had multiple possible places which may have been used for cooking, but no fixed fireplace, and no one place was used for the entire lifetime of the house. Nevett points out that houses frequently had a "complex pattern of spatial usage", with rooms being used for multiple purposes.
Family
Men
A man was the head (kyrios, ) of the household. The kyrios was responsible for representing the interests of his oikos to the wider polis and providing legal protection to the women and minors with whom he shared his household. Initially the kyrios of an oikos would have been the husband and father of offspring. However, when any legitimate sons reached adulthood the role of kyrios could, in many instances, be transferred from the father to the next male generation. When a son was given his portion of the inheritance, either before or after his father had died, he was said to have formed a new oikos. Therefore, new oikoi were formed every generation and would continue to be perpetuated through marriage and childbirth.<ref name= Parker > </ref>