A Stone circle is an ancient monument, usually dated from the late Neolithic - early Bronze Age, that is, c.3000-1500 Bc. They are not always precisely circular and often forms an ellipse, or a setting of four stones laid on an arc of a circle. The number of stones can vary between four and 60 purposely erected standing stones, and often contain burial pits or chambers. A stone circle is different from a henge or isolated monolith, although often encountered together in a single location. Their precise function will always be open to debate, no one knows what they were built for, but the popular theory suggests a practical purpose could exist in the form of use as astronomical marker points for use in determining calendar related event, such as the equinox (autumn and spring) or solstice (summer and winter).
A Henge is a Neolithic earthwork that has a ring bank with a ditch on the inside of the bank. This means that the henge can not be considered as having a defensive purpose.