● oxfordlearnersdictionaries.com

Oxford Learner's Dictionaries

● dictionary.cambridge.org

Cambridge English Dictionary

● www.merriam-webster.com

Merriam Webster

● www.ldoceonline.com

Longman Dictionary of Contemporary English

● collinsdictionary.com

Collins Dictionary

● www.ahdictionary.com

American Heritage Dictionary

● en.wiktionary.org

Wiktionary

● ielts.org

IELTS: International English Language Testing System

● www.ets.org/toefl

TOEFL: Test of English as a Foreign Language

● www.ets.org/gre

GRE: Graduate Record Examinations

● www.gutenberg.org

Project Gutenberg: over 70,000 free e-books

● www.ted.com

TED: Ideas worth spreading

● learnenglish.britishcouncil.org

British Council: Learning English

● www.ili.ir

Iran Language Institute