addableadj.

1663 E. Waterhouse Fortescutus Illustratus 60 So the Philopher calls that perfect..to which there is nothing to be expected addable, because virtue is perfection it self.

1678 J. Hawkins Cocker's Arithm. iv. 33 The first number in every addition is called the Addable number, the other, the number or numbers added, and the number invented by the Addition is called the Aggregate or Sum.

1755 S. Johnson Dict. Eng. Lang. (ed. 2) Addable adj., that which may be added. Addible is more proper.

1798 Locke's Ess. Human Understanding I. ii. xvii. 195 The confused incomprehensible remainder of endless addable [ed. 6 (1710): addible] numbers.

1827 J. Bentham Wks. (1843) VII. vii. iii. 178/2 To these it may now and then happen that the evidence ex collatione may be addable.

1851 G. Brown Gram. Eng. Grammars i. 193 Whether we ought to write tenable or tenible, reversable or reversible, addable or addible.

1908 Philos. Rev. 17 514 Would it not be equally true to say that for 1 and 2 to be given, they must be addable?

1998 Independent 9 Apr. (Educ. Plus section) 2/3 It believes it can assign numbers to achievements and experiences from the cradle to the grave. These, too, will presumably be treated as if they are addable in various ways.