-HOW COME/-WHY
How come means the same as WHY but keep an eye on the sentence order in questions:HOW COME it’s an informal way to say ‘Why’.

-How come YOU ARE sad?
-Why ARE YOU sad?

-How come you’re leaving?
-Why are you leaving?

This website has been posted for teaching English Grammar and Vocabulary through video lessons and example sentences showing how to use these grammar points and words in a sentence with the meaning in the authantic examples.