When you write an essay, consider your audience--typically, college professors or high school teachers. They will expect you to use a more extensive vocabulary in your writing than you would during normal speech. However, avoid wordiness, technical jargon and misused words. For example, your professor may consider the use of "the fact that" instead of "because" an attempt to pad your essay to meet a minimum word count.
The University of North Carolina defines jargon as technical language used by experts in a particular field. Too much jargon will make your argument less clear. Misused words can change the meaning of a sentence and weaken your position.
Prepositions describe the relation of a noun, pronoun or noun phrase to the rest of a sentence in terms of time or location. Prepositions come before the noun they describe and after a verb. According to the Bull's Eye Business Writing website, you can end a sentence with a preposition--contrary to common wisdom--but don't add extra prepositions to the sentence.
Conjunctions join two simple sentences, phrases, clauses or words together to create a longer sentence that reads more easily. place conjunctions between the items they connect, not at the beginning of a sentence. Conjunctions such as "and," "but," and "or," when used to combine complete sentences, require a comma before them. When connecting words or phrases, don't use a comma. Have no more than three independent clauses--complete sentences--connected by commas because otherwise it reads as a run-on sentence.