In deciding on a level of formality, consider both your subject and your audience. Does the subject demand a dignified treatment, or is a relaxed tone more suitable? Will readers be put off if you assume too close a relationship with them, or might you alienate them by seeming too distant?

For most college and professional writing, some degree of formality is appropriate. In a job application letter, for example, it is a mistake to sound too breezy and informal.

Informal writing is appropriate for private letters, personal e-mail and text messages, and business correspondence between close associates. Like spoken conversation, informal writing allows contractions (don’t, I’ll ) and colloquial words (kids, kinda). Vocabulary and sentence structure are rarely complex.

In choosing a level of formality, above all be consistent. When a writer’s voice shifts from one level of formality to another, readers receive mixed messages.

Words such as commenced and elucidated are inappropriate for the subject matter, and they clash with informal terms such as sucker pitch and fast windup.