There are three related types of Neolithic earthwork that are all sometimes loosely called henges. The essential characteristic of all three types is that they feature a ring bank and ditch, but with the ditch inside the bank rather than outside. Due to the poor defensive utility of an enclosure with an external bank and an internal ditch, henges are not considered to have served a defensive purpose (cf. circular rampart). The three types are as follows, with the figure in brackets being the approximate diameter of the central flat area:

1. Henge (> 20 m). The word henge refers to a particular type of earthwork of the Neolithic period, typically consisting of a roughly circular or oval-shaped bank with an internal ditch surrounding a central flat area of more than 20 m in diameter. There is typically little if any evidence of occupation in a henge, although they may contain ritual structures such as stone circles, timber circles and coves. Henge monument is sometimes used as a synonym for henge. Henges sometimes, but by no means always, featured stone or timber circles, and circle henge is sometimes used to describe these structures. The three largest stone circles in Britain (Avebury, the Great Circle at Stanton Drew stone circles and the Ring of Brodgar) are each in a henge. Examples of henges without significant internal monuments are the three henges of Thornborough Henges. Although having given its name to the word henge, Stonehenge is an atypical henge in that the ditch is outside the main earthwork bank.
2. Hengiform monument (5 = diameter = 20 m). Like an ordinary henge except the central flat area is between 5 and 20 m in diameter, they comprise a modest earthwork with a fairly wide outer bank. Mini henge or Dorchester henge are sometimes used as synonyms for hengiform monument. An example is the Neolithic site at Wormy Hillock Henge.
3. Henge enclosure (> 300 m). A Neolithic ring earthwork with the ditch inside the bank, with the central flat area having abundant evidence of occupation and usually being more than 300 m in diameter. Some true henges are as large as this (e.g., Avebury), but lack evidence of domestic occupation. Super henge is sometimes used as a synonym for a henge enclosure. Examples of henge enclosures are Durrington Walls and Mount Pleasant Henge.