Sometimes it can be inappropriate (or boring) to write realistic dialogue. If you are Aaron Sorkin or Shakespeare or R.A. Salvatore you probably don’t want your characters having humdrum conversations littered with everyday grammar. You’re creating a world, a fantasy kingdom, an idealized version of reality. Your characters’ speech, word choice, syntax and rhythms should reflect that.
Write A Story Containing Stylized Dialogue
The key to making this work is that you must remain consistent in tone through out the piece. If your main character sounds Shakespearean at the beginning, make sure he sounds that way in all his big set pieces.
Of course, you can puncture the style for comic effect but this works best if you break out of the style sparingly.
And just because everyone speaks in a formal or jargon-laden, or poetic manner, doesn’t mean that all your characters should sound the same: far from it. Even in Shakespeare, you still have people who are florid and poetic, and people who are earthy, coarse and abrupt.
Give it a try, have some fun. You may find you’re adding a style of dialogue to your repertoire that you can pull out in moments of high drama in your future writing. If it goes badly, at least you’ll have discovered some of the pitfalls of writing this way and can avoid them in future.