WordBranch 字首字根字尾字典 is a free iPhone application developed by YiLin Tsai, designed for English word learning. This app, evolving since 2016, is a comprehensive tool suitable for various standardized tests like GRE, GMAT, SAT, ACT, TOEFL, IELTS, TOEIC, as well as local exams and self-improvement. It boasts the most complete and accurate collection of word prefixes, roots, and suffixes.

The key features of WordBranch include a quick dictionary lookup for over 30,000 decomposable words, totaling 100,000 words, pronunciation with KK phonetic symbols, YouTube videos explaining prefixes, roots, and suffixes, comprehensive tables for reference, a wide range of prefixes, roots, and suffixes, and the ability to create flashcards for quick word review, especially tailored for exams like GRE and TOEFL.