Trader (noun)

1. A person who buys and sells goods and commodities for profit.
2. A person who is engaged in trading as an occupation or business.

Origin:

From old english "trædere".

Examples:

1. He is a trader in the stock market.
2. The trader bought low and sold high.
3. The trader made a profit on the deal.
4. The trader specialized in rare coins.
5. The trader had a booth at the market.