I use this app (and the Spanish equivalent) quite frequently and love them both. They offer great translations as well as audio pronunciations. I want to suggest three features that would make these apps 5-star worthy:
1- Support for the new iPhone X and iPad Pro display sizes in order to truly take advantage of each
2- The ability to either search both sides (English to X and X to English) at the same time, or the ability to switch between the two searches without having to re-type the search query term to speed up searching as sometimes one may forget to check which dictionary is selected, and if it's the wrong one, switching erases the term requiring it to be typed in again to search the other dictionary
3- iPad multitasking support. The ability to simply slide-over into these apps or to have it sitting side-by-side with a document or book would be a wonderful, time-saving convenience