Duolingo

I have personally used this app for learning and came across following 1) Best User interface :- it is easy to operate even a non smartphone savvy can use it . 2) It has covered the basics pretty well . 3) Step by step learning methodology which makes it a great app . 4) Number of languages available for learning . 5) It will help in proper pronunciation also that i personally found really great . 6) Compatible with all the versions of android ,so any one can use it .

1) You nee a fast internet connection to use it properly. 2) It became boring sometimes learning a new language. 3) No option of saving tough words to access or recall later. 4) No option available for changing the themes which makes it quite monotonous 5) should have been more interactive to make learning more fun. 6) should have come up with games and puzzles to make learning fun.

Well every software has it's pro and cons depending upon the user ,this one is no doubt far better then the rest available in this segment .it has great usability, with good features set , you can relay on it for learning with no doubts in mind , pricing is amazing as it is free on android ,with a great customer service thus all in all a great package.