Translation of "Thumb" in Chinese

My grandmother has a green thumb.

我祖母是個園藝巧手。

As a rule of thumb, you should plan on one pound of beef for every two guests.

一般來說，你應該為每兩個客人準備一磅牛肉。

The hand has five fingers: the thumb, the index finger, the middle finger, the ring finger, and the pinky.

人的手有五个手指: 拇指、食指、中指、无名指和小指。