economical : 指正当使用财物，强调节省，避免浪费。
- There's increasing demand for cars that are more economical on fuel.
- What's the most economical way of heating this building?
thrifty : 侧重节缩开支，积蓄收入。
- They have plenty of money now, but they still tend to be thrifty.
- Lei Feng, always thrifty, had saved this sum from his allowances.