Dollar (noun)

1. The standard unit of money in the United States, Canada, Australia, and other countries.
2. A coin or banknote worth one dollar.
3. Used to refer to any monetary unit of similar value in other countries.

Origin:

Middle english doler, dolour, from old french doler, ultimately from germanic.

Examples:

1. I need two dollars to buy this candy.
2. He earned a dollar an hour for his work.
3. The price of a dollar was going down.
4. He had a pocket full of dollar bills.
5. A dollar is worth more in some countries than in others.