Diphtherial is an adjective that describes something related to or characteristic of diphtheria, a potentially deadly bacterial infection that affects the respiratory system. Some synonyms for diphtherial include infectious, contagious, dangerous, lethal, fatal, virulent, and deadly. These words emphasize the severity and life-threatening nature of the disease and its potential to spread from person to person. They also imply the need for urgent medical attention and preventive measures. Other related words include bacterium, toxin, vaccine, and immunization, which are all associated with the prevention and treatment of diphtheria. In summary, diphtherial and its synonyms convey the seriousness and urgency of this infectious disease.