The nasalising of these diphthongs adds to the unpleasant effect.
If they appear as proper diphthongs, they follow the rule of diphthongs.
In diphthongs the breathing and accent are written over the second vowel.
All words have as many syllables as they have vowels and diphthongs.
Anglo-Saxon diphthongs are written as e, e with stress on second vowel.
There are as many syllables in a word as there are separate vowels and diphthongs.
In a similar way, the diphthongs ei and ai are not universally distinguished.
The diphthongs are pronounced with the stress on the first element.
The diphthongs and œ are sounded like e: as cdo, pronounced ce'do.
How do we know whether or not these compounds are diphthongs or digraphs?
late 15c., from Middle French diphthongue, from Late Latin diphthongus, from Greek diphthongos "having two sounds," from di- "double" (see di- (1)) + phthongos "sound, voice," related to phthengesthai "utter, speak loudly."