It comes from the Latin word "mittere", which means "to send".
Here's how it breaks down:
* Ad- is a prefix meaning "to" or "toward".
* Mit- is the root word meaning "to send".
* -ion is a suffix forming nouns, indicating an action or process.
Therefore, "admission" literally means "the act of sending toward". In the context of admission, it refers to the act of being allowed to enter or participate in something.