Formal diction refers to word usage that’s commonly found in formal scenarios, and it doesn’t necessarily reflect the way people speak. Such situations can include language in presentations, formal gatherings and scholarly journals. This form is mostly used in situations that address highly educated audiences. Formal diction, also called elevated language, often uses more abstract or figurative words, and it privileges words with Latinate roots, such as “edify” and “beguile.” Formal diction uses elegant, extravagant and sophisticated vocabulary, and the words generally are polysyllabic, meaning they have more than one syllable.
Informal diction is word usage that is grammatically correct but appropriate for more informal settings. This kind of language is commonly used when addressing a familiar or a more comfortable specific audience, such as your friends, and you can use this diction in personal letters or documents with a conversational or entertaining tone. Informal diction includes slang and colloquial diction; slang uses newer words that can be impolite, and colloquial speech uses words commonly found in everyday speech. Such language might use the word “wise up” instead of “edify” and “jerk your chain” in place of “beguile.” Along with slang and colloquial diction, vulgarity is also a form of informal diction -- that is, language lacking in taste and refinement.
Standard diction is closely related to informal diction, but with minor differences. Such diction is often used when addressing a well-educated audience; it's the level used for college papers and business communications. Instead of using the slang term "wise up," standard diction would use “learn.” Standard diction is also referred to as Standard American English.
Connotations are a key element of diction, as they are used to suggest and display emotional meaning. A connotation can give the listener or reader an impression that's created by their associations with a word rather than by its dictionary definition. This type of diction can be broken into two types of connotations, positive and negative. A positive connotation can help leave the audience with a positive attitude while a negative connotation will do the opposite.