a thousand and one

a Determinative

— A is used when the following word could be any of a certain type. Compare "A book I saw on the shelf" and "The book I gave you yesterday".

a Noun

— A is the first letter of the alphabet. The letter "a" comes before "b". — In some schools, an A is a very high grade. Ron got an A on his earth science test.

thousand Determiner

— (ordinal thousandth) The number 1,000. Julius Caesar lived about two thousand years ago.

thousand Noun

— The number 1,000.

and Conjunction

— You use and to talk about two things at once. I like singing and reading. Mary and Jane went on a holiday together. — You use and when you are listing a few things and you are now on your last item of the list. I like singing, reading, cycling and playing soccer. I used to like this girl from my class as she is pretty, gentle and caring. — And is used when you are putting two sentences together. She came into the store, shouted at the cashier, and left. — Used to show what happened after something else. The alarm went off and I woke up. — And is used to join certain numbers together. Two hundred and thirty-five people went missing after the earthquake.

one Determinative

— (ordinal first) The number 1. We have one nose and one mouth.

one Noun

— The number 1. One is the smallest whole number.

one Pronoun

— One is a singular pronoun which means "someone" or "people". It is used more often in formal writing. It is easy to see the difference if one looks closely enough.