economic(al)

1.现在economic作“经济（学）上的”解，economical作“节约的”解，如economic help（经济援助）和economic point of view（经济观点），economical use（节约的用法）和economical meal（节约的一餐）。Adam Smith's economic doctrine, the economic structure of society, economic independence, economic crisis, economic espionage（经济间谍），economic penetration（经济侵入）等表达方式里必须用economic。

2.economical后面接of。例如：She is economical of her time.

3.相当于economic和economical的副词都是economically。