M2-c: When to use a or an
M2-cUse a (or an) with common singular count nouns that refer to “one” or “any.”
If a count noun refers to one unspecific item (not a whole category), use the indefinite article, a or an. A and an usually mean “one among many” but can also mean “any one.” (See the chart in M2-d.)
The noun dictionary refers to “one unspecific dictionary” or “any dictionary.”
The noun apartment refers to “any apartment close to the lake,” not a specific apartment.