commerce 多指大规模的买卖或易货关系。
trade 普通用词，含义广。既可指某种具体的.商业又可指广泛的贸易。
bargain 多指买卖双方通过谈判、协商就商品质量、数量、价格等项达成协议所成的生意。
deal 口语用词，指买卖双方经过交涉达成协议成交。
bargain的例句：
1. They prefer to bargain with individual clients, for cash.
在现款方面，他们更愿意同散户打交道。
2. They need hostages in order to bargain with the government.
他们要想同政府讨价还价就得有人质。
3. Fresh salmon is a bargain at the supermarket this week.
这周超市的新鲜鲑鱼特价销售。
4. Clothes are the best bargain, with many items marked down.
买衣服是最划算的，许多衣服都降价了。
5. Majorca and Ibiza are tops for holiday bargain-hunters in June.
对于实惠型度假者来说，马略卡岛与伊维萨岛是6月份的绝好选择。
6. "It's a fabulous deal, a real bargain."
“这桩买卖真让人难以置信，绝对合算。”
7. At this price the wine is a bargain.
这种葡萄酒卖这个价真是很便宜。
8. More and more criminals will agree to plea-bargain.
越来越多的罪犯会同意接受认罪辩诉协议。
9. The so-called bargain was just a big con!
这种所谓的减价商品只不过是个大骗局!
10. The bargain prices are expected to entice customers away from other stores.
低廉的价格意在把顾客从其他商店吸引过来。
11. You can drive a hard bargain in the free market.
在自由市场上你可使劲地讨价还价。
12. The women in the market often bargain away for hours.
女人们经常在市场里一连几小时讨价还价。
13. Don't bargain on getting any support from her; she's very selfish.
别指望从她那里得到什么援助, 她很自私。
14. We do not like to bargain with you about the prices.
我们不想就价格问题与你讨价还价。
15. This shirt was a bargain — only ￡15 in a sale.
这件衬衫是便宜货,大减价时只卖十五英镑。