keeper及er表示被动

一些像employ这样的动词有employer和employee两个名词，而keep的名词只有keeper，keepee不是词。美剧FRIENDS和TBBT里出现了He/she is a keeper. 此处keeper应解释为person who is worthy of *being* kept, 值得*被*留住的。主动“留”的有beekeeper bookkeeper gatekeeper housekeeper innkeeper shopkeeper timekeeper zookeeper等。

类似的例子还有roaster和broiler.【牛津高阶英汉双解词典】roaster: 适合*被*烤着吃的鸡；broiler: young chicken reared for broiling or roasting. 词典也懒得写成being broiled. 不过broil还有become very hot的意思，原因未知。:-)

of的用法也有点类似：【牛津高阶英汉双解词典】an outrageous invasion of privacy *对*隐私权的粗暴侵犯。这和the responsibility of the employees中of的含义不同。再如：

The Invasion of Normandy was the invasion and establishment of Western Allied forces in Normandy, during Operation Overlord in 1944 during World War II.

On June 6, 1944, the Battle of Normandy began.

The D-Day operation of June 6, 1944 brought together the land, air and sea forces of the allied armies in what became known as the largest invasion force in human history.

The Norman Invasion of England: The Norman Conquest of England. The Vikings invade England in the late 900s. The story of the Norman conquest of England begins in the late 900s, when the English king, Aethelred, found his kingdom attacked by Viking invaders, as Alfred the Great had seen England invaded a hundred years earlier.

【LDOCE】invasion - when the army of one country enters another country by force, in order to take control of it