HOW COME? It means ‘‘why” in a informal way. (something happened or reasons)
EXPRESSION FOR CONVERSATION: HOW COME?
- ”Why” is formal. (writing or speanking);
- ”How come” is informal. (speaking).
e.g. How come + subject + verb + object ?
How come I am not the president? (informal) = Why am I not the president? (formal);
i.e. Why + verb + subject + obeject ?
Why did you arrive yesterday? (formal) = How come you arrived yesterday? (informal).