Diction refers to the choice of words and style of expression that a writer or speaker uses. The diction in your speeches or literary works affects the tone and how your message is received by your audience.

For instance, formal, high-level vocabulary can convey professionalism and authority, suitable for academic or legal contexts. 

Informal, colloquial language can make your communications more relatable and accessible; it's ideal for casual talks or personal blogs.

An example of effective diction might be a lawyer choosing precise, technical terms in court to ensure clarity and adherence to legal standards.

A comedian might use slang and informal expressions to connect with the audience.

Experiment with different levels of formality and word choices to see how they affect the tone and impact of your communications.