formal sum

Meanings

1. An expression which looks like a sum but where the symbol + has a purely symbolic role, in the sense that the summands cannot be meaningfully combined.
2. An element of a free abelian group or vector space regarded as a sum of basis elements.
3. A sum of an infinite sequence of numbers considered as an indeterminate object, in the sense of being subject to certain algebraic manipulations but not necessarily convergent.