Compound sentences consist of two, equal or balanced independent clauses, joined by a connective or conjunction. They are great for building arguments and linking ideas. They use theme and rheme to build cohesion across paragraphs.
Note: in a compound sentence, the clauses cannot be reversed in order.
Compound Sentence:The probewas placedin the cylinderandthenitwas usedto measure the flow.
SFL description:ParticipantProcessCircumstanceConnectiveCircumstanceParticipantProcessCircumstance
TG description:Subject Definite Article, NounFinite VerbAdverbial phrase of place Preposition, Definite Article, NounConjunctionSignpost of time3rd person singular Subject PronounFinite verb (passive, simple past tense)Verb in the infinitive plus Object (Definite Article plus Noun)
(Note that these three elements, then it was, can be implied rather than written in full.)