Science communication is a growing area of practice and research. During the past five decades, the number of definitions has steadily increased. But what actually is science communication? In what ways is it different to scientific communication, public awareness of science, public understanding of science? The author reviews the literature to draw a comprehensive definition of scientific communication, including these related terms. A unifying structure is presented and a contemporary definition of science communication positioned within this framework. Scientific communication comprises means, channels of communication, institutional activities that provide circulation of scientific information in society. It is a two way process of communication between scientific community and society. Scientific communication is an information sharing and / or a scientific dialogue between scholars and between scientific community and society about science in an (inter) active way through different strategies adapted to specific target groups. The functions of scientific communication are: awareness, increase knowledge, opinion formation, change attitude and behavior change etc.