Halliday & Matthiessen (2014: 648):
There is no very clear line between meronymy and hyponymy, especially with abstract terms; and a given set of items may be co-hyponyms of one term but co-meronyms of another – for example, chair, table, bed are ‘kinds’ (hyponyms) of furniture, but ‘parts’ (meronyms) of furnishings; forward, half-back, back are ‘kinds’ of players but ‘parts’ of a team, and so on. But since either relationship is a source of lexical cohesion it is not necessary to insist on deciding between them.