economic / economical

Economic ADJ 经济的;经济上的
Economic means concerned with the organization of the money, industry, and trade of a country, region, or society.意为与国家、地区、社会或个人经济有关的：

the economic aspects of having children
生育孩子在经济方面的问题

Economical ADJ-GRADED 经济的;省钱的
Something that is economical does not require a lot of money to operate. For example a car that only uses a small amount of petrol is economical .意为经济实惠的、节俭的、节约的：

It is usually economical to buy washing powder in large quantities.
大量购买洗衣粉通常要省钱些。