I have been using the Collins Spanish Dictionary - Complete and Unabridged 9th Ed. v. 1.2.1 app. on my iPhone practically every day for a month, and it is truly outstanding. First, it is very complete. I have yet to find a word it did not cover. Second, the quality of the entries is excellent, with many, many examples of usage that are very helpful. Third, the pull-down conjugation function, providing full conjugation for every verb, makes it unnecessary to have one of those "501" Spanish Verbs books. Fourth, and by no means last, it is fast and easy to use. Although this dictionary is more expensive than most of others, in my opinion it is fully worth price and the dictionary to have if you want a comprehensive Spanish/English dictionary.