The crossword solution for the term 'PREFIX DENOTING STRAIGHT' is ORTHO, which is a five-letter word. The prefix 'ortho-' is derived from the Greek word 'orthos, ' which means 'STRAIGHT.' It is used in many scientific and medical terms to denote something that is STRAIGHT or upright. For example, an orthopedic surgeon specializes in treating musculoskeletal problems, while an orthodontist specializes in straightening teeth.