Learning new words every day is a nice habit to pick up. It is not only good for your brain but could help improve your communication skills over time. You could always learn new words by reading books or trying word games. Apps like these help you build your vocabulary more effectively:
Word Vault: a pretty handy application that helps you keep track of the new words you learn and helps you test yourself to make sure you remember them for longer.
Wordflex Touch Dictionary: one of the best dictionary apps we have tested. This iPad app provides you with a tree-based view of words and gesture-based interactions. Complete audio pronunciations for words are included.
Crosswords: a pretty awesome app that brings a ton of crossword puzzles to your iOS device so you can learn new words as you try them. You can keep your puzzles synced across your devices and download new ones every day. Need some help? Crosswords provides you with that as well.
There are plenty of other apps you can use to build your vocabulary. The above tools are user-friendly and help you learn new words faster.