As the School grew, more students were allowed to attend provided that they paid their own fees and lived in the town, outside the College's original buildings. These students became known as Oppidans, from the Latin word oppidum, meaning town. The Houses developed over time as a means of providing residence for the Oppidans in a more congenial manner, and during the 18th and 19th centuries were mostly run by women known as "dames". They typically contain about fifty boys. Although classes are organised on a School basis, most boys spend a large proportion of their time in their House. Each House has a formal name, mainly used for post and people outside the Eton community. It is generally known by the boys by the initials or surname of the House Master, the teacher who lives in the house and manages the pupils in it.