Brand voice is the consistent character of the words a business uses when it speaks or writes. It is shaped by choices such as vocabulary, sentence length, formality, and how directly the brand addresses people. Tone can change with the situation: a service apology should sound different from a launch announcement while still feeling like the same organization.
A useful voice guide gives a few clear traits and examples of what those traits sound like in emails, web copy, proposals, and customer replies. Test the examples with the people who will use them. REX’s Robinson Roof Solutions case study describes developing a brand personality and voice alongside positioning.