I'm confused around the sentences:
- What are differences between...
- What are the differences between...
What are differences between a circle and a sphere?
What are the differences between a circle and a sphere?
I know, that we use article a to speak about single countable noun, and also single countable noun mentioned for the first time, or speak about something single and countable in general. With plurals the article is omitted, as in the first excerpt.
From the other hand, we use article 'the' with countable and uncountable nouns when we'd like to speak about something specific.
So,IMHO both of these excerpts are correct, but I always faced only the second one, and the first one almost never. I found out the question, but it is slightly different.