Invasion is a word that comes from Latin. Originally, it meant that something goes in (as in military occupation) of a foreign territory. So far, the following uses are known:
- Military: Getting troops into enemy territory and occupying that territory.
- Others: Sometimes, biologists speak about an invasive species. There might be locust swarms invading, or that some algae spread far more rapidly in new territory.
One of many examples is the importing of rabbits to Australia. As they had no enemies, they did what rabbits do best. They multiplied. To get rid of them, people then thought about importing foxes as well.