A dunam (Ottoman Turkish, Arabic: ; ; ; ), also known as a donum or dunum and as the old, Turkish, or Ottoman stremma, was the Ottoman unit of area analogous in role (but not equal) to the Greek stremma or English acre, representing the amount of land that could be ploughed by a team of oxen in a day. The legal definition was "forty standard paces in length and breadth", but its actual area varied considerably from place to place, from a little more than 900 m<sup>2</sup> in Ottoman Palestine to around 2 500 m<sup>2</sup> in Iraq.
The unit is still in use in many areas previously ruled by the Ottomans, although the new or metric dunam has been redefined as exactly 1 000 m<sup>2</sup>.
The name dönüm, from the Ottoman Turkish ( ), appears to be a calque of the Byzantine Greek stremma and had the same size. It was likely adopted by the Ottomans from the Byzantines in Mysia-Bithynia.
The Dictionary of Modern Greek defines the old Ottoman stremma as approximately , but Costas Lapavitsas used the value of for the region of Naoussa in the early 20th century.
In Bosnia and Herzegovina and in Serbia the unit is called the dulum (ôÃÂûÃÂü) or dunum (ôÃÂýÃÂü). In Bosnia and Herzegovina a dunum (or dulum) equals . In the region of Leskovac, south Serbia, one dulum is equal to . In Albania it is called a dynym or dylym and is equal to .
In Bulgaria, the decare (ôõúðÃÂ) is used, which is an SI unit, literally meaning 10 ares.
In Cyprus, a donum is or 14400 square feet. In the Republic of Cyprus older Greek-Cypriots also still refer to the donum using the local Greek Cypriot dialect word ÃÂúìûõà[skales], rather than the mainland Greek word stremma (equivalent to a decare). However, since 1986 officially Cyprus uses the square metre and the hectare.
A donum consists of 4 evleks, each of which consists of or 3.600 square feet.
In Greece, the old dönüm is called a "Turkish stremma", while today, a stremma or "royal stremma" is exactly one decare, like the metric dönüm.
In Iraq, the dunam is .
In Israel, Palestine and Turkey, the dunam is , which is 1 decare. From the Ottoman period and through the early years of the British Mandate for Palestine, the size of a dunam was , but in 1928, the metric dunam of was adopted, and this is still used today in Israel and Palestine.
The Dubai Statistics Center and Statistics Centre Abu Dhabi use the metric dunam (spelt as donum) for data relating to agricultural land use. One donum equals .
Other countries using a dunam of some size include Libya and Syria.
The Byzantine Greek stremma was the probable source of the Turkish unit. The zeugarion (Turkish çift) was a similar unit derived from the area plowed by a team of oxen in a day. The English acre was originally similar to both units in principle, although it developed separately.