How works

Build vocabulary with activities that adapts to each student

a picture of students smiling facing each others

A smart, award-winning adaptive engine has crafted a smart, award-winning adaptive engine that helps learners systematically improve their vocabulary.

We understand how students learn words

Learners have answered over 7 billion questions on and we use this data to understand how each individual masters (and forgets) new words. With millions of questions answered daily, our engine continually fine tunes itself for anyone at any level.

Personalized learning

With each question a student answers, the Challenge evaluates their knowledge on a 20-level scale and adjusts the student's learning plan to meet their needs. We use each individual's vocabulary level and their past answers to identify the unique gaps in their vocabulary knowledge. The Challenge then systematically challenges them with questions selected just for that learner.

The right words

By comparing answers from all of's learners, the Challenge identifies trends and common gaps for different levels on our scale. We can identify which words students are ready to learn and which words they are likely to need help with at each level. The Challenge incorporates these words into the student's daily vocabulary exercises.

The right questions

As students answer basic questions correctly and progress toward mastering a word, the Challenge poses harder questions that stretch the student's knowledge. With dozens of questions for each word, the Challenge is able to test nuance and peripheral meanings in addition to a single definition. With ten different types of questions—including questions based on images, synonyms, and real world examples—students learn each word's multiple meanings and understand them in context.

The right timing

Knowledge and recall can decline over time, so our adaptive engine also takes into account the timing of learning a word. The Challenge tracks how long it has been since a learner was asked about a word and automatically includes brush-up questions. With this spaced repetition, support for long-term retention is built into our model.