In Inuujingajut (the standard alphabet of Nunavut) long vowels are written as a double vowel.

So, a rising tone is sometimes indicated indirectly by writing a double vowel:

Double consonants and double vowels also go a long way toward revealing a cryptogram's meaning.

The writing system includes four simple vowels, and four double vowels:

British woollen is a further exception due to the double vowel (American: woolen).

Pre-empt is hyphenated to split the double vowel, much as co-operate once was.

(Op-Ed, June 6), about presidential aspirants' names, calls to mind other aspects: the double vowel and alliteration.

There are the double vowels in Coolidge, Hoover and the two Roosevelts.

The following examples illustrates the case of double vowels.

However, I would put a hyphen between the double vowels as an aid to pronunciation: re-engineering.