Longman Dictionary of Contemporary English
Wikipedia
A common market is usually referred to as the first stage towards the creation of a single market. It usually is built upon a free trade area with relatively free movement of capital and of services, but not so advanced in reduction of the rest of the trade barriers.
A single market is a type of trade bloc in which most trade barriers have been removed (for goods) with some common policies on product regulation, and freedom of movement of the factors of production ( capital and labour) and of enterprise and services. The goal is that the movement of capital, labour, goods, and services between the members is as easy as within them. The physical (borders), technical (standards) and fiscal (taxes) barriers among the member states are removed to the maximum extent possible. These barriers obstruct the freedom of movement of the four factors of production.
A unified market is the last stage and ultimate goal of a single market. It requires the total free movement of goods, services (including financial services), capital and people without regard to national boundaries.
Usage examples of "single market".
March was a poor land, sparsely populated, with a single market town, Blantize.
The March was a poor land, sparsely populated, with a single market town, Blantize.
I thought, however, as I drove back to Pixhill with the Single Market booklet on the seat beside me, that I was as far as ever from understanding why anyone should need or want to fix hiding-places under my lorries.
Mitteleuropa: Axis Europe, a single market stretching from the Atlantic coast to beyond the Urals.