Latin, mercatum, portus.
Domesday Book records 60 markets, 48 of them in Great Domesday. It is certain, however, that this is a very incomplete tally. Only three markets are named for the whole of circuit 3, and all are in Bedfordshire. It is equally improbable that Cornwall had five markets but Dorset none, or that Somerset had seven but Wiltshire only one. Even allowing for its devastated condition, it seems unlikely that there was only one market in the whole of Yorkshire.
The majority of these markets were on rural manors. Little information other than the value to their lord is normally recorded; but some of these values were high enough - £11 is the highest figure - to indicate a considerable volume of trading. Another indication of trading activity is the entry for Tutbury in Staffordshire (STS 10,1), where it is recorded there were '42 men who live only by their trading; with the market, they pay £4 10s'.
At least a third the recorded population did not have sufficient land to support a family. Many must therefore have depended upon market activity for their livelihood. There is every reason to believe that trading activity is massively understated in Domesday.
For more detail, see H.C. Darby, Domesday England (1977); R.H. Britnell, The commercialisation of English society (1993); and Edward Miller and John Hatcher, Medieval England: towns, commerce and crafts, 1086-1348 (1995).