Art is the expression of emotion. It is subjective, and involves creativity and inspiration. Science is the study of the universe. It is objective, and consists of systematic hypotheses.
Design is more than superficial visual appearance. To design, is to solve a problem. It could be to beautify a website, which seems to need just an artistic touch, but the expected result is to have a better usability and to improve user experience. When hiring a designer, you expect him to solve a problem.
Design is no longer just a service. It can influence the success of a company. Many great companies have adopted design thinking. Designers should step up to understand the business, find out the problem, and provide a solution.