|part of speech:
||any one of a group or kind.
A horse has hooves.Somebody call a doctor!The magician told her to pick a card.
||one, as a quantity.
He dumped a cup of flour into the mixing bowl.
||one; used to introduce one particular thing or person of a group or kind, but one which is not known to the listener or is not important to identify.
I walked home with a friend from school.A man with a suitcase got on the bus.