Erica: Matt is so weird! He's always invading my personal space.
Christina: Me too! He always stands too close. Do you think he just does it to girls?
Erica: I don't know. Let's ask Tom. Hey Tom!
Christina: Erica and I have a question. We noticed that Matt sometimes gets a little too close. Does he do that to you as well?
Tom: Yes! He apparently doesn't understand what personal space is.
Meaning: "Personal space" is an invisible border around a person that is considered unacceptable to cross. While the exact size varies by person and culture, most people feel uncomfortable if someone else stands closer than approximately 2 feet from him/her. In the above example, Erica, Christina and Tom all agree that Matt often stands too close; most likely, Matt's idea of personal space is just smaller than theirs. Notice that Erica uses the verb "invade" to describe the way Matt crosses this invisible line; most people think of the area directly around themselves as their own, personal space, and it is an invasion of privacy to cross it.
Here is another example:
Daniel: I hate the subway after work!
Daniel: Everyone is so crammed in there. I get claustrophobic*.
Helen: Weird. I hate when other people invade my personal space too, but it doesn't really bother me on the subway. I guess it's because I know it's not their fault.
Daniel: You're lucky. I flip out when strangers are that close.
*claustrophobia is a fear of small spaces.
Meaning: In this case, Daniel and Christina are talking about the crowded subway. For most people (like Helen), personal space invasions don't bother them as much when it's caused by a crowd; however, some people (like Daniel) are so bothered by personal space invasions that they become frightened.
This idiom is from LSI's book "Reading Horizons," which is used in the Level 6 Reading classes. For more information, please visit http://www.languagesystems.com/