“经贸合作”翻译成economic and trade cooperation, 这是习惯用语.economic is an adjective,trade can be an adjective.In dictionary, Definition of trade:adjective18.of or pertaining to trade or commerce.19.used by, serving, or intended for a particular trade: trade journal.20.Also, composed of, or serving the members of a trade: a trade club. People use economic to avoid a second confused meaning of Economy: economy can be used as a synonym for efficiency (效率的代名词). Fuel economy measures how many miles per gallon a vehicle consumes. For this meaning, we use economical instead of economic as the adjective form.谷歌搜索 "economic and trade" 124,000,000 results"economy and trade" 684,000 results