Transparencies are materials that allow light to pass through them, making the objects they cover appear visible. There are several synonyms for the word "transparencies," including clear film, acetate slides, viewgraphs, slides, and overhead transparency film. Clear film is used for printing images such as photographs and graphics. Acetate slides are a form of transparent plastic sheet used for overhead projectors. Viewgraphs is a term used to describe transparency slides that show charts, diagrams, and other visual aids. Slides, as a general term, refer to any transparent material used for projection or display. Lastly, overhead transparency film is a specific type of acetate slide used for displaying text and images via overhead projectors.