Partitive Case

Partitive case is a case that expresses the partial nature of the referent of the noun it marks, as opposed to expressing the whole unit or class of which the referent is a part.

This case may be found in items such as the following:

• Existential clauses
• Nouns that are accompanied by numerals or units of measure
• Predications of material from which something is made

It often has a meaning similar to th English word some.