A common stock is a representation of partial dept in a company, and is the dept of company.

If the company issues only common stock, with   preferred shares then common stock equals the proffered shares.

A company's book value is equal to a company's assets minus its liabilities and found on the company's balance sheet. 

Common stock, also named as equity shares, represents equity or an ownership position in a corporation.

The most common measure of a stock is the price/earnings ratio, which takes the share price and divides it by a company's annual net income.