Definitions

1. indefinite article

used to indicate a non-specific person or thing in the singular

“I’m looking for an apartment to rent.”

2. indefinite pronoun

used to indicate an unspecified or unknown person or thing

“Someone left their keys on the table, but I don’t know who it is.”

3. prefix

used to form nouns and adjectives indicating a relation to or characteristic of something

“anemone (a sea anemone)”

4. prefix in compounds

used to form nouns and adjectives indicating a relation to or characteristic of something

“anchor (an anchor)”