Register and Style
Based on situational factors (see chapter about speech situations), different speech situations influence the speaker's choice of a language variety. Registers are functional varieties; they ‘function’ in different types of speech situations. Accordingly, a register is a linguistic variety regarded as appropriate to use in a particular speech situation. Register is usually associated with a particular speech situation (Kortmann 2005: 255f).
Legal language, or Legalese, is an example of a register normally only used in the field of law and justice.
The choice of register in different types of speech situations is termed ‘situational variation’. The term ‘style’ is also occasionally used to refer to situational variation. However, it includes variation in grammatical structures, too. It is less predictable and more dependent on personal preferences than register (Kortmann 2005: 256).
There is a terminological distinction between register and style. Both are associated with a specific speech situation but whereas register often refers to the specific vocabulary chosen and expected in connection with a particular speech situation, style also includes grammatical variation (cf. Kortmann 2005: 255ff).
(For more information on registers see Textual Variation: Registers, Jargon, Slang).