S / substĭtūtĭo
noun

substĭtūtĭo

gen. substĭtūtōnis · gender feminine · decl. 3rd
substituo, II..
a putting in the place of another; substitution
In gen., a putting in the place of another, substitution, Arn. 3, p. 104.—
the appointment of a second; alternate heir
In partic., in jurid. lang., the appointment of a second or alternate heir, Gai. Inst. 2, § 174 sq.; Dig. 28, tit. 6.