Traditionally, this was a term used to describe an area of grassland used for communal grazing by a defined group of common-right holders (see commons). Greens were (and sometimes still are) fringed by the houses and farmsteads of the common-right holders. Archaeological evidence suggests that some greens started to be established in the 11th century, but with greater numbers following in the 12th and 13th centuries. The largest greens, up to about 530 acres in extent, were on the wide and poorly-drained clay interfluves(qv) of north Suffolk. Many greens were enclosed in the 18th and early 19th centuries, but often their outlines survive as ‘ghosts’ in the landscape. The surviving greens frequently have great biodiversity value as areas of undisturbed ancient grassland.Since the Commons Registration Act of 1965, greens and commons have become legally distinct: commons are subject to communal grazing rights, but greens are used for exercise or recreation – but in the past the terms were interchangeable. In south Suffolk, the term tye(qv) is a synonym for a green.