So, I was taught that we use 'fruits' when referring to different kinds of fruit. So why is 'fruit' singular in this dictionary entry:
pith: a white substance just under the outside skin of oranges and similar fruit.
What is it that I haven't gotten?
It looks wrong. But I am no authority more than that fruit is defined in dictionaries as both singular and plural, though I don't recall ever seeing 'fruit are...'
You know, I think that's because of what I said. The plural 'fruit' is for some of the same kind, but 'fruits' for some of different ones.
As is the case about 'fish' and 'fishes'. Â
But, still, I don't know why that definition is with 'fruit'.
I do not see anything wrong with the dictionary's sentence.
I'll even go further and say, "That fruit basket contains citrus fruit, pitted fruit, pineapple fruit, breadfruit, and bananas."
BTW, the Google Ngram viewer has 18,200 entries for "fruit are" from 1-1-1965 to 12-31-2000. That period has less than half the rate of the full two centuries to which the viewer defaults. (I realize there could be many duplicates in the number quoted.)
Emmett
Fruit happens like this:
1--Fruit as an article:
    A fruit is on the plate, an orange.
    Two fruits are on the plate, one an orange, the other mango.
2--Fruit as a kind of fruit:
    A fruit is selected for our new planet, and we pick orange.
    Two fruits are selected for our new planet, orange and mango.
3--Fruit as different from other things:
    Fruit is down the aisle from meat.
    Fruits are down the aisle from meat.
4--Fruit as metaphor:
   Fruit/Fruits of out labors.
Your dictionary definition fits category 2 above: fruits.
pith: a white substance just under the outside skin of oranges and similar fruits.
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I would like to know, which dictionary?