205 ILCS 620/1-5.10
"Surplus" means the aggregate of (i) amounts paid in excess of the par value of capital stock and preferred stock; (ii) amounts contributed other than for capital stock and preferred stock and allocated to the surplus account; and (iii) amounts transferred from undivided profits.
(from Ch. 17, par. 1551-5.10)
(Source: P.A. 86-754.)