Elements Serving As Interpersonal Theme [Defined]

Halliday & Matthiessen (2014: 108):

1. [interpersonal] Vocative. This is any item, typically (but not necessarily) a personal name, being used to address.
2. [interpersonal] Modal/comment Adjunct. These express the speaker/writer’s judgment on or attitude to the content of the message.
3. [interpersonal] Finite verbal operator. These are the small set of finite auxiliary verbs construing primary tense or modality; they are the unmarked Theme of yes/no interrogatives.