The amount of formality with which you write should be defined by the expectations of your audience and the purpose of your writing. A cover letter for a job application or a college academic essay, for example, would be written in a formal manner. An email to friends may use a more informal tone. Formal writing tends to use long sentences and complex words that require analysis and interpretation. In general, formal writing is difficult reading and often seems like gibberish to many people. On the other hand, informal writing is simple and clear. It uses short sentences and common words that can be understood immediately by most readers. In addition to the level of formality, the context in which you write can affect the choice of words that you use. For example, if you are writing to someone you do not know well, you will want to use simpler language. At the other end of the spectrum, if you are writing something very formal and stately, using refined English won't be necessary; instead, read about formatting paragraphs and pages here. Finally, your own personality may also influence the choice of vocabulary. If you are writing in a formal manner, but using words and phrases that don't seem appropriate, your reader will notice this and may feel uncomfortable reading what you have to say.