I recently learned the word quasi and found it's very similar to semi. I looked up in the dictionary and found many examples, like quasi-governmental. Out of curiosity, I searched "semi-governmental" in Google books and the result surprised me. There are a lot of "semi-governmental" being used. What's the differences between quasi and semi? Can I use them interchangeably?
semi- literally means half (as in a "semi-detached house") while quasi- means almost. In common usage you can use either one interchangeably, and Wiktionary lists each one as a synonym for the other.
Semi as a noun refers to specific usages, like a semi-trailer or semi-detached house, and you would not use "quasi" in those places.