He's wonderfully fit for his age.

他年纪那么大，可身体出奇地好。

The food was not fit for human consumption.

这食物不适合人吃。

This food is not fit for human consumption.

这种食物不适合人食用。

Fitness is relative; one must always ask "Fit for what?"

适宜是相对的；始终必须问问：“适宜什么？”

Of the seven bicycles we had, only two were fit for the road.

我们的七辆自行车中，只有两辆适合这种路。