Halliday & Matthiessen (2014: 452):
Parataxis is the linking of elements of equal status … Both the initiating and the continuing elements are free, in the sense that each could stand as a functioning whole. In principle, the paratactic relation is logically (i) symmetrical and (ii) transitive. This can be exemplified by the ‘and’ relation. (i) ‘salt and pepper’ implies ‘pepper and salt’, so the relationship is symmetrical; (ii) ‘salt and pepper’, ‘pepper and mustard’ together imply ‘salt and mustard’, so the relationship is transitive.