The best way to learn proper English is to read news report, and watch news on TV. Watching TV shows is a great way to learn casual English, slang words, understand culture reference and humor. If you have already watched these shows then you may recall the words used in the following dialogs.

...but your father was in the auditorium
at your high school GRADUATION...
The Big Bang Theory Season 6, Episode 19

Sweetie, you know you're supposed
to wear clothes under the GRADUATION gown.
The Big Bang Theory Season 8, Episode 22