Wide vocabulary knowledge is associated with proficiency in reading comprehension and scores on tests involving comprehension. Yet assessments show that U.S. students at various grade levels have demonstrated no improvement in their vocabulary knowledge since 2009. Literacy expert Timothy Rasinski and colleagues argue that students need improved vocabulary instruction, especially because learning content area words--which represent new concepts and are essential to ensuring students' have strong comprehension and build background knowledge--is difficult. Instruction must be multidimensional and extend beyond dictionary definitions to be meaningful. The authors show how basing vocabulary instruction on Greek and Latin roots can help, and point readers to resources. They outline a three-day sequence of instruction, taking 10 minutes a day, for helping students learn word roots that are the foundation of many academic words. Students not only grasp vocabulary, they learn how to infer the meaning of new words by analyzing the parts of that word.