Is PR an art or a science ?

PR is more of a science as you can measure the outcomes and results in numerical terms. If the PR is doing fine then the business will be able to carry out the operations more smoothly and if there are hurdles that means PR needs to do better.

It is a combination of both. Pursuing a professional relation with employees and clients ia an ART while using different methods for business internal and external analysis is a science.

Marketing is an art because you have to convince other people and create loyalty in their minds.

Its combination of both. New techniques, analysis, endevours needed.

Both , but when you applied a system used before , you well decrease the lost of time and build on the previous experience. 

It depends on the way you pursue

public relations is the art and social science of analyzing trends, predicting their consequences, counselling organization's leaders

Marketing is Art because Marketing is about creating a demand for your product.

Understanding the science behind the art is absolutely central to building effective and successful communication campaigns.

PR is an art that is followed by passion

Edward Bernays, one of the first and most prolific writers about public relations, was a strong proponent of the notion that public relations should be considered a science. More specifically, he called it “an applied social science” and equated it with other applied sciences in his landmark book The Engineering of Consent and many other publications. This is a view that’s been controversial from the very beginning. It prompted mixed responses when it was first proposed, and continues to draw mixed reviews today.  Public relations cannot and does not use some scientific and statistical techniques, or that its outcomes are totally unpredictable. Public relations is becoming more knowledge-based, more measurable, but it will always have to deal with the unpredictability and contrariness of human nature that will forever keep it from being totally predictable. Since it deals with people and the interactions and relationships they have with one another, public relations cannot be an exact science. Its practice can be an art. It will continue to have rules and guidelines, tried and true techniques, and standards of excellence, but they will never be fully codified. Nor will human intuition and feelings ever be totally eliminated from its practice. But, the more sophisticated, more experienced, and more human its practitioners become, the more artistic, elegant, and effective its practice will be.