Clostridium difficile, commonly known as C. difficile, is a bacterium that can cause severe and sometimes fatal infections. There are several synonyms for this pathogen, including Clostridioides difficile, Clostridium difficile infection (CDI), and C. diff. While C. difficile can be found in the environment, it is most commonly transmitted in healthcare settings, where it can spread rapidly from person to person. The bacterium is notorious for causing severe diarrhea, abdominal pain, and other symptoms in patients with weakened immune systems. Fortunately, with proper infection control measures and prompt medical treatment, many cases of C. difficile can be successfully treated.