The purpose of this study was to measure the mathematics-vocabulary performance of 3rd graders to determine if performance differences existed among English learners (ELs) and non-ELs with and without mathematics difficulty (MD). Using screening data from a large-scale intervention study, we categorized students into four groups based on equation solving and word-problem performance: no MD, equation difficulty, word-problem difficulty, or equation and word-problem difficulty. Within these four categories, we compared student performance between ELs and non-ELs. Results showed ELs scored lower than non-ELs across all groups. Both ELs and non-ELs with equation and word-problem difficulty demonstrated lower performance on the mathematics vocabulary measure than students with only equation difficulty or word-problem difficulty. Findings indicated ELs and students with MD have limited mathematics vocabulary knowledge and may require focused instruction on the language of mathematics. [This paper was published in "Reading and Writing Quarterly: Overcoming Learning Difficulties" v36 n2 p124-141 2020 (EJ1249760).]