descriptor

2. In computing, a piece of data that identifies or describes a file, resource, or memory area.

The program uses a file descriptor to keep track of the open document.

3. In linguistics, a word that describes or modifies a noun, such as an adjective.

In the phrase 'red apple', 'red' acts as a descriptor.

4. In chemistry, a term or symbol that identifies a specific feature of a molecule, such as its shape or structure.

The stereochemical descriptor shows how the atoms are arranged in space.