When proofreading a document, you want to ensure your message is clear. You have an idea in your mind, you transform it into words, and you hope the person reading it understands.
The words we choose are often too conversational. If you nonchalantly said certain words or phrases in conversation, your idea could make perfect sense and not disrupt the cohesiveness of the discussion. In writing, even if an informal tone is appropriate, little differences can affect your message’s clarity and effectiveness. You want to choose formal words even amidst a humorous, witty, or casual subject matter.