Suppose the following sentence:
- When the sun comes in the morning; the sky is blue.
Are "When the sun comes in the morning" and "the sky is blue" two clauses of the sentence? So, is it correct to use a semicolon?
Yes, those are both clauses, but it is not correct to use a semicolon. You must join them with a comma.
This is because those are not two independent clauses (essentially, two complete sentences). Rather, the first one is governed by the conjunction when.