The hot-air balloon took off. It was as buoyant in the air as a cork (软木塞) in water.
把热气球比作水中的软木塞，说明“buoyant ”的意义：“漂浮；浮力。”
6．根据同义词的替代
Venus rotates retrograde, or “backwards”, spinning in the opposite direction of its orbit around the Sun.
由“backwards”这一替代词得知“retrograde”的意思：“向后的。”
7．有时也可根据一般性常识/生活经验猜测词义
The door was so low that I hit my head on the lintel.
门太低，我的头撞在“lintel门楣”上了。
He got on the motorbike, I sat behind him on the pillion, and we roared off into the night.
由经验得知“pillion”是motorbike的“后座、后鞍。”
8．也可根据词形构造猜测词义
More recently, scientists have documented an alarmingly high occurrence of frogs with malformations.
form是词根, formation“形式”，mal-:构词前缀，可表示“坏、恶、不良”，还可表示“不、不正常、不当、非法。”malformation的意思就应该是“畸形。”更多的例子如：malnutrition: 营养不良；malconduct:（公职人员的）胡作非为；maladjustive: 引起失调的；不利调节的。
当然，要想做到这一点，就必须掌握英语常用的前缀、后缀及词根的意义。