The process of learning a language requires that long-term memory stores the meanings of thousands of words encountered across a variety of situations. These word meanings form a network of associations that, influenced by environmental factors such as word frequency and contextual diversity, cause behavioral effects on measures such as lexical decision and naming times. We investigate the development of recognition priming as a function of explicit knowledge after repeated training and testing on a novel vocabulary. By varying the word frequency and contextual diversity of the training input, and examining learning trajectories as well as semantic knowledge effects, we shed light on which environmental factors most influence performance in language acquisition. Contextual diversity and entropy–the uncertainty about a word’s referents–are the two strongest factors predicting primed recognition times, and play a role along with frequency and context familiarity in predicting explicit learning.