Thanks, garpike. I'm editing the comment I made a half hour ago. I checked 'ai in my dictionary." ʻAi: 1. nvt Food or food plant, especially vegetable food as distinguished from iʻa, meat or fleshy food; often 'ai refers to specifically to poi." So DL has it right.
Thanks for this information. I don't have a proper Hawaiian dictionary; Wiktionary is pretty reliable for major languages, but less so for more minor ones.
It's interesting that a general word for food has acquired a more specific meaning—usually, this happens the other way round.
DL seems not to require that we literally state "the" every time we see ka/ke even though ʻōlelo requires that or an equivalent to mark the noun. I am under the impression that to translate "Poi or fish" from English into Hawaiian, youʻd have to insert articles (noun markers).
That is exactly the idea of how Duolingo approaches teaching languages. It's just like how children learn (with the exception of tips & notes).
Another good question. Poi is a food, a paste made from the pounded corm of the taro plant. Taro is a very important plant in Hawaiian culture. It is seen as the older sibling of the Hawaiian people, and nourishes us as an older sibling would. It is traditionally the staple crop, and because of this, the word "ʻai" which means food in general can also refer to taro or poi.