Given an entity as input, output another entity which is part of the input entity. These are entities of meronym. In linguistics, meronymy is a semantic relation between a meronym denoting a part and a holonym denoting a whole. In simpler terms, a meronym (i.e., output entity) is in a part-of relationship with its holonym (i.e., input entity).

Q: propellant

A: combustion modifier
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Q: calla

A: long - petiole , basal leave
****
Q: vein

A:
carbon dioxide
****