Par value describes the face value or dollar value of a security; the nominal value is indicated by the issuing party.
The nominal value of a share is the initial value of the share indicated in the certificate for this share; The face value of a bond is the dollar amount that must be paid to the investor at the maturity of the bond.
The actual market value of a stock or bond cannot be reliably determined from its face value because there are many other influencing forces such as supply and demand.