The order of acquisition of various aspects of word knowledge is underexplored. Thus, this study examined learner performance with a number of aspects of word knowledge in an attempt to see whether they form an implicational scale in terms of an accuracy order. A total of 283 English as a Second Language students were tested on their knowledge of five aspects of word knowledge. Implicational scaling analysis was utilized to determine whether the components were scalable. The findings formed a scalable accuracy order. The accuracy order of the aspects of word knowledge examined in this study from easier to more difficult include: knowledge of the written form based on the spoken form, knowledge of the spoken form based on the written form, knowledge of the written form based on the meaning, knowledge of the spoken form based on the meaning, knowledge of spelling based on the spoken form. These findings suggest a number of implications for vocabulary acquisition as well as vocabulary teaching and learning.