Duolingo Blog | All posts from Duolingo What’s the International Phonetic Alphabet, and how do I use it? Dear Duolingo: Why does Japanese have three writing systems? 11 chess terms every beginner needs to know A guide to 3rd grade math topics A guide to 4th grade math topics A guide to 2nd grade math topics A guide to 7th grade math topics A guide to 5th grade math topics A guide to 8th grade math topics A guide to 6th grade math topics When to use “tú” and “usted” in Spanish How to use infinitives in English (and over 130 examples!) How to conjugate English verbs in the simple present 100+ regular and irregular verbs in English 2 ways to form the future tense in English How to use the present progressive in English Types of English verbs: modals, auxiliaries, and more The complete guide to English verbs Past participles in English: how to form them and when to use them How we made our Korean course better, smarter, and more fun How Duolingo teaches writing skills Chess openings: What is the Chigorin Defense? Chess openings: What is the Catalan Opening? Chess openings: What is the King’s Indian Attack? Chess openings: What is the Slav Defense? Chess openings: What is the Queen’s Gambit? Chess openings: What is the Vienna Game? Chess openings: What is the Trompowsky Attack? Chess openings: What is the French Defense? Chess openings: What is the King’s Indian Defense? Chess openings: What is the Pirc Defense? Chess openings: What is the Scotch Game? Chess openings: What is the Nimzowitsch-Larsen Attack? Chess openings: What is Petrov’s Defense? Chess openings: What is the London System? Chess openings: What is Bird’s Opening? Chess openings: What is the King’s Fianchetto Opening? Chess openings: What is the Ruy Lopez? Chess openings: What is the Bogo-Indian Defense? Chess openings: What is the Caro-Kann Defense? Chess openings: What is the Réti Opening? Chess openings: What is the Grünfeld Defense? Chess openings: What is the Benko Gambit? Chess openings: What is the Benoni Defense? Chess openings: What is the Sicilian Defense? Chess openings: What is the Dutch Defense? Chess openings: What is the Modern Defense? Chess openings: What is the Scandinavian Defense? Chess openings: What is the English Opening? Chess openings: What is the Nimzo-Indian Defense? Chess openings: What is the Grob Opening? Chess openings: What is the Italian Game? Chess openings: What is the King’s Gambit? 33 chess openings you should know Chess openings: What is Alekhine’s Defense? How to use definite and indefinite Italian articles How we built an automated unit test generation pipeline for iOS Dear Duolingo: Is English a difficult language to learn? How a simple code change reduced CPU usage by 97% Your guide to chess notation