Final answer:
The term 'Open stock' refers to the option of purchasing individual dinnerware pieces, as opposed to sets.
Step-by-step explanation:
The term that indicates that dinnerware may be purchased by the piece is Open stock. Unlike place setting, which typically includes individual tableware for one person, or bulk set and combo pack, which imply sets of items bundled together, open stock allows customers to buy individual dinnerware items. This option is especially beneficial for those who may want to replace a broken plate or customize their tableware collection without having to purchase an entire new set.