Some disagreements with diphthongs.
The textbook says that in English "..ou is a not a diphthong, though it is a digraph." p. 5.
Although the following disagreement does not affect the Greek, it does affect the understanding of English. The statement itself has the seeds of the disagreement in the word "though".
The status as a diphthong depends on where the ou is.
- not a diphthong -- e.g.
- short u - tough, slough (verb)
- long u - through, croup, slough (noun)
- short a or aw - thought, bought, ought, sought
- a diphthong -- e.g.
- ow as in owe - though
- ow as in cow - thou, bough
(My condolences to foreigners trying to learn English as a second language.)