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.

I can't believe you kissed my sister
with MOTH mouth.
The Big Bang Theory Season 4, Episode 6

Don't worry, little MOTH.
The Big Bang Theory Season 7, Episode 5

- Yeah, you are. It's just my MOTH...
- If I could interject again.
The Big Bang Theory Season 3, Episode 11

...with MOTH wings and an exoskeleton.
The Big Bang Theory Season 2, Episode 6