It's not an app but it is the best Tagalog dictionary I've seen that's available in the US (the only one more complete is a two-volume set from National Bookstore that you'd probably spend $100+ on before shipping). It breaks words down to roots and affixes, which I've found is the best way to understand how to then put these together into words and sentences. I recommend it to all my students. http://www.amazon.com/Tagalog-English-English-Tagalog-Standard-Dictionary-Pilipino-Inggles/dp/B004RZBJ9U/ref=sr_1_7?s=books&ie;=UTF8&qid;=1445382556&sr;=1-7&keywords;=tagalog+dictionary

oops, link http://www.seasite.niu.edu/Tagalog/tagalog_verbs.htm

I've used this a little bit. Seasite is worth exploring, there are some good detailed explanations of grammatical concepts

Try this: http://learningtagalog.com/grammar/index.html