We are thinking of entering GRE iPhone/iPad market and I kept an eye on what's going on there for awhile. I can't recommend any particular app as I didn't test them well but it seems that different types of vocabularies are very popular, such as
"
Kaplan GRE Exam Vocabulary Flashcards and Reference Guide"
"GRE and GMAT Vocabulary builder"
"Smart Vocab (GRE)"
"PowerVocab GMAT and GRE" is a new app.
Some other providers offer questions and I didn't try them. At the same time many of them have GMAT apps too and are not popular at all. So, I would recommend you to search for "GRE" in the appstore and try apps only within top1-10. Very rarely you can find a good app that has lower position than 10.
Month ago I tested one XYZ (not GRE) Vocabulary app that claims all words were manually picked by XYZ experts and tutors. When I ran an analyzer through all official tests, some words were not even mentioned in official tests and some had statistical occurrence as any other 50K+ English words. I don't claim that all apps are bad but some really are. So, approach them with a grain of salt. Reading reviews is useful but for many reasons they could be biased.
Anyway, as I mentioned at the beginning, GRE vocabularies should be good.
If you have other questions related iPhone/iPad apps, feel free to pm me.
Best,
Walker
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