group of settlements linked by continuous urban area

A conurbation is an urban area that includes a number of cities, towns and villages which, through population growth and expansion, have physically merged to form one continuous built up area. It is a sort of agglomeration.

SchipholHaarlemmermeerVelsenDelftThe HagueAlphen aan den RijnZaanstadLelystadHilversumGoudaZoetermeerAmersfoortAlkmaarHaarlemDordrechtLeidenAlmereRotterdamPort of RotterdamPort of RotterdamPort of RotterdamPort of RotterdamPort of RotterdamUtrecht (city)Amsterdam
Clickable schematic map of the Randstad, a big conurbation in the Netherlands

A metropolitan area usually combines one or several conurbations.