The study set out to examine the partial word knowledge of native speakers, L2 advanced, and intermediate learners of English with regard to four word features from Richards' (1976) taxonomy of aspects describing what knowing a word entails. To capture partial familiarity, the participants completed in writing a test containing low and mid frequency content words, accompanied by a word knowledge scale. The analysis showed that there were three distinctive patterns of partially familiar vocabulary but their distribution across the three groups was quite different, which indicated that partial knowledge was linked to different word features across the three proficiency groups. It was also of interest to explore whether the participants maintained similar associative connections for their frontier words and whether a word association task would capture partial familiarity. Overall, participants' associative domains for frontier words did not reveal any consistent associative behavior that would distinguish between proficiency groups.