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.

That could not be less ARBITRARY.
If it varied even slightly...
The Big Bang Theory Season 2, Episode 18

...that the sun's position relative
to ARBITRARY constellations...
The Big Bang Theory Season 1, Episode 1

Look at Planck's constant.
People say that's ARBITRARY.
The Big Bang Theory Season 2, Episode 18