"Wahyi" literally means inspiration, revelation; suggestion, to point out a thing to someone, to put a thing into the mind of someone secretly, letter, writing; something revealed or written or the idea inspired or revealed; saying; commandment; to dispatch a messenger to someone; to speak with someone secretly; to urge; voice. In Islamic terminology, wahyi means communication of idea, command and information from Allah to a chosen human being, conveyed either directly or through supernatural agencies like angels.

"Ilham" literally means to inspire; to put a thought or an idea into the mind of someone. In Islamic terminology, ilham means inspiration of an idea or information from Allah to any chosen person.

It will appear from above that while ilham is limited to unspoken and unwritten inspiration, wahyi is used for spoken as well as unspoken and written as well as unwritten inspiration and revelation.

Every religion which believes in God believes in revelation.

http://islamist.faithweb.com