TENOR:The relationship between writer and audience- there status ( who produced it for who?) "Dear Madam"
FIELD: The topic -what it's about E.G it's an apology letter.
FUNCTION: The purpose-why it was written E.G to entertain, to persuade.
MODE may affect language use such as grammer because the mode can be written in different formalitys therefore, the use of punctuation changes for example when the mode is electronic (sending a text to a friend) because it's a text between you and a friend it become informal as it's not work related or professional.
TENOR may affect language use due to the relationship between the writer and audience and who has a higher status for example if there's a speech between a police officer and a young girl the police officer will have a higher status because of his authority.
FIELD may affect language use due to the topic, again for example if the field of a text is about an article on a president it's formality will have to be formal because the topic is of such high authority and so important ,however ,if the topic is about friends it's less formal.
FUNCTION may affect language use for example if the purpose of a text is to persuade it will use persuasive language in order to achieve that function.