This article discusses the concept of a share in the German, Polish, Swiss, and European law on co-operatives. It begins with the definition of a share according to the German law on co-operatives. There, a share is a value expressed in figures and defined in the Charter. This figure reflects financial participation of a member in the co-operative. However, it is not the very essence of membership rights. In the Polish law, a share in the co-operative has two meanings. It is a value expressed in figures and defined by the Charter. Such share, contributed by the member, reflects his/her participation in the co-operative assets. E.g. it is taken into account when losses or surpluses of the co-operative are distributed. Subsequently, the article discusses the concept of a share in the co-operative in the Swiss law. There, contrary to the German system, a share in the co-operative is not just a figure, but the very essence of rights and obligations, both material and co-operative, arising from the setting up of the co-operative equity. The share of a member is a part of his/her membership and can be transfered. Subsequently, the article discusses the concept of a share and the concept of a balance-sheet share in the Austrian draft bill on co-operatives developed by the Ludwig Bolzmann-Institut für Rechtsvorsorge und Urkundenwesen an der Universität Wien. The article presents also the concept of a share in the co-operative according to the the European Council Regulation. The equity of a European Co-operative is made of shares. Their face value is defined in the Charter. The share is not identical with the membership. It is a registered security.