Derivational affixes create variations of meaning within word families, so learner knowledge of how derivations transform meaning can boost comprehension. This paper looks at second language (L2) learners’ receptive knowledge of unknown members of word families in order to better understand how learners encounter new forms of words with derivational affixes. Overall, the participants were able to move within word families at a receptive level but often had difficulty with non-target, sentential syntax of the British National Corpus examples. It was also found that words-per-minute was a predictor of the participants’ ability to move within word families. Finally, participants were challenged when moving from one derivational affixed target to another.