There is a more widened explanation the matter in question:
Share = a particular separate part or portion into which the capital of a company is divided, thus, e.g. a company may have a capital of &1 million divided into two million shares of 50 p each. Each share gives the person who possesses it, called a member or shareholder, a part of the ownership of the company, which means that he has the right to receive a share in the profits and to share in its management. In the USA although the capital of a stock corporation, the equivalent of a company, is divided into shares, they are called stock and their holders are called stockholders.
Stock = a store of good for sale
We have a large stock of men’s clothes.
The company has too much money tied up in stock.
Stock = a portion of the capital of a company that has converted its fully-pai shares into units, usually of &100 nominal value.
Capital stock = the capital of a company that has been subscribed by its members.
In Britain, the capital of a company that ha converted its shares into units, usually of &100 nominal value. The capital of a company must always first be issued in the form of shares, each of which has a nominal or face value that cannot be divided into smaller units.