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.

There is an inherent AMBIGUITY
in the word "dinner."
The Big Bang Theory Season 1, Episode 3

...is AMBIGUITY in a contract
benefits the party that did not draft it.
The Big Bang Theory Season 4, Episode 21