Educators will be interested to know that the average probability to learn unknown words from context is about 15 percent. Under natural reading circumstances students will spontaneously derive and learn the meaning of about 15 words of every 100 unknown words they encounter.
Swanborn, M. S. L., & de Glopper, K. (1999). Incidental word learning while reading: A meta-analysis. Review of Educational Research, 69, 262-286.
