Countable or Uncountable nouns are very confusing.
Especially, when it comes to fruit and vegetables - they are very similar to me- why is fruit uncountable and why are vegetables countable?
How about these sentences?
Apples are fruit.
An apple is fruit.
Tomatoes are vegetables. ( whether it is true or not

)
A tomato is a vegetable.
To lead a healthy life, you need to replace fatty foods and sweets with fresh fruit and vegetables.
Are all of the sentences correct?
Or would you correct some sentences?