Playing word games will help increase your vocabulary.  7 Little Words is a very popular free word game app for iPhone/iPad and Android, but it’s a little too difficult for most people learning English.  However, there is a kid’s version – with easier vocabulary – that is fun and challenging to play. Here’s an example:  The hint for word #5 is “time off from school”, and the word is VACATION.

7 Little Words for Kids is available for iPhone/iPad (99 cents) and Amazon Kindle Fire ($2.99).
If you have an Android phone, you can look at this list of the 10 Best Free Word Games for Android.