Yeah, I messed up my point, sorry. I was pretty sure that neither "ei" nor "ie" are English diphtongs while they both are in German.
German "ei" always sounds like the English 'eye' or simply 'I' German "ie" sounds like the English 'ee' as in 'see'.
Never in my life have I heard an Englishman say "Reikspiel" so I was curious how any of y'all would pronounce it.
Also, apologies to Michael for derailing the thread
For no particular reason you've sent me down the IPA rabbit hole, and apparently ei in English really is a dipthong, as in eight and weight thus:
ˈeɪt
And of course an entirely different one in height.
ˈhaɪt
A dipthong being internationally defined as anything requiring the movement of the vocal apparatus between two vowel sounds in a single syllable, even if those sounds are heard as a single sound by native speakers. (At least according to the wiki IPA dive. In my primary school days I think it was described a bit less elegantly, but I still believe they called it a dipthong. Interestingly, the ie in believe is a monopthong.)
All of these are IPA transcriptions of American English pronunciations, mind. And IPA is such a weird, weird thing anyway. (The only people I've known who genuinely study it are opera singers, though I suspect linguists and philologists probably do as well.)
The wiki article gives "No highway cowboys" as an example sentence where every syllable contains a dipthong. (Even no, where in American English the o fades subtly into an oo.)
But I can easily believe that English has fewer than German, say. And they clearly differ quite a lot by regional accent anyway.