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.

It's a STRATEGIC maneuver.
The Big Bang Theory Season 4, Episode 22

without a STRATEGIC thought in his head.
Game of Thrones Season 3, Episode 3

It is his once the war is over and we
have no further STRATEGIC need for it.
Game of Thrones Season 3, Episode 6

The governor's bodyguards.
And the place has STRATEGIC importance.
Money Heist Season 3, Episode 2