Research (Nation, 1990) suggests it takes 4-6 instances of high-quality exposure to commit new vocabulary to memory. The learning sequence on Mapper includes multiple exposures for every word across the curriculum.
A session on Mapper includes the assessment (pre/post tests), explicit teaching and learning activities for the sequenced words within a set.
For a word to be included in a session, it must be ready for teaching. To be ready for teaching a word must have a word quiz and either a definition or a description and example.
There are a variety of different activities that can be created for a word to increase the number of exposures and the variety of contexts that the word is taught in.