The following sites will help you increase your English vocabulary.
1. Merriam-Webster’s Learner’s Dictionary more from www.learnersdictionary.com This is an American English Dictionary for Students of ESL. It’s free, but you need to create an account.
2. LITTLE EXPLORERS Picture Dictionary by EnchantedLearning.com http://www.enchantedlearning.com/Dictionary.html This is an English Picture Dictionary arranged by categories. You can translate from English to several major languages.
3. Meta-analysis – Definition and More from the Free Merriam-Webster Dictionary http://www.merriam-webster.com/ This site is an online dictionary, thesaurus, and has medical terms, videos, word-of-the-day, quizzes and games. There is an English-Spanish dictionary as well.
4. The Internet Picture Dictionary English, French, German, Spanish, Italian http://www.pdictionary.com/ This site has flashcards, fill-in-the-blanks, word scrambles, spelling for all different categories of things such as fruit, animals, colors, numbers.
Heinle’s Newbury House Dictionary of American English