Cumulative reference

In semantics, cumulative reference is the model-theoretic property that characterizes a mass noun like water in terms of the cumulative structure of its extension.

Example
If w1 and w2 are two bits of water in the extension of water, then the sum of w1 and w2 (i.e. the result of putting w1 and w2 together) is also in the extension.

Comment
Plural count nouns also have the property of cumulative reference.

Link
Utrecht Lexicon of Linguistics