IPA: /ˈtreɪdə/
KK: /ˈtreɪdər/
A person or ship that buys and sells goods, often for profit, in various markets.
The trader made a significant profit by buying stocks at a low price and selling them when the price increased.
Trader → It is formed from "trade" (from Old English *træd*, meaning a path or way, which evolved to mean a business or exchange of goods) and "-er" (meaning a person who). A trader is a person who engages in the business of exchanging goods.
Think of someone who follows a 'path' ('træd') to engage in 'business' or 'exchange' — that's what a trader does.