- an acute, highly contagious bacterial disease causing inflammation of the mucous membranes, formation of a false membrane in the throat that hinders breathing and swallowing, and potentially fatal heart and nerve damage by a bacterial toxin in the blood. It is now rare in developed countries because of immunization.
- The disease is caused by Corynebacterium diphtheriae
mid 19th century: modern Latin, from French diphthérie (earlier diphthérite), from Greek diphthera 'skin, hide'
In the past, diphtheria was correctly pronounced with an f sound representing the two letters ph (as in telephone, phantom, and other ph words derived from Greek). In recent years, the pronunciation has shifted and today the more common pronunciation, no longer incorrect in standard English, is with a p sound. Nevertheless, the f sound remains the primary pronunciation.