I don't write too many reviews about iPhone apps but this one is truly amazing.
First off, as of version 6.1 fully supports iPhone 4 and iOS 4.2.
There are a few really good Japanese dictionaries out there like Kotoba and Japanese, and those dictionaries have some great special features like Japanese certification practice/test features, example sentences, Japanese to English dictionaries, grammatical information, flash card systems with saved kanji, or stroke order or even pronunciation.
While Daijisen doesn't have the types of features listed above, Daijisen stands apart as a dictionary for Japanese neo-natives and natives. In sheer depth alone, Daijisen is the clear leader. While other dictionaries are akin to good sized paperback dictionaries, Daijisen feels more like a very large hard cover desk reference.
Some of the essential features include a full jinmei/chimei jiten (critical if you struggle name cards from people you meet), and surprisingly, full descriptions of very modern lingo like "twitter" as well as many modern Japanese colloquialisms. There's also a simple photo reference though that could benefit from more photos and some additional features. But the biggest feature is likely the proprietary hand-writing recognition. The other dictionaries require using the native Chinese character hand-writing recognition built into the iPhone which works okay but misses many common kanji no matter how cleanly or how many attempts I try. Daijisen's proprietary hand-writing recognition easily outclasses the iPhone native Chinese version and makes far fewer mistakes.
There is no Japanese to English dictionary, and romanized Japanese words won't be looked up (e.g. typing in "watashi" will yield no results). There is an Eiwa (English-Japanese) dictionary and that is very mission critical for me. Even better, there's a full Japanese thesaurus.
Daijisen is clearly designed for someone who is advanced enough to not need a dictionary geared towards non-Japanese. So clearly this isn't for everyone, but u won't find a more complete Japanese dictionary out there. As a neo-native I find that I need many of the features in other dictionaries like Kotoba or Japanese, but I also find those dictionaries lacking in some critical capabilities that only Daijisen can provide. So assuming you don't need the advanced JLPT and stroke order features of Japanese ($15.99), I highly recommend getting Kotoba (free) and Daijisen ($16.99) for neo-native Japanese language proficient individual.
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