Fifth criterium: The economic town term

If you want to specify the town purely economically, MAX WEBER (2001) defines it as a settlement whose inhabitants lives predominantly on the yield of non-agricultural, for example commercial or trading industry.
A further feature that has to be mentioned is the presence of a certain versatility of the existing trades. The economical torn term covers "a settlement of humans, who are dependent for their own maintenance to products of other agricultural work":

1. various trades as predominant source of income of the settlers, independent of the agriculture
2. a constant market

These criteria seem to be necessary, but they do not permit the sharp definition to a town however.