Research consistently highlights the critical role of vocabulary in reading comprehension and literacy development. According to Shanahan (2005), "Vocabulary knowledge is one of the best predictors of reading comprehension," emphasizing that a great about of vocabulary allows readers to make sense of texts more effectively (p. 24). "Vocabulary contributes to reading fluency by enabling students recognize and understand words automatically, reducing cognitive load and allowing for deeper engagement with the text" (Manyak, p. 17). 

Students also show that vocabulary is not acquired in isolation but through exposure to rich and meaningful context. "Students learn words best when they encounter them multiple times in different contexts," a principle supported by Beck, McKeown, and Kucan (2013, p. 15). This suggests that effective vocabulary instruction should include direct teaching and opportunities for students to experience words in diverse situations. 

Furthermore, limited vocabulary knowledge can significantly hold back a student's reading comprehension and overall academic success. As noted by Stahl and Nagy (2006), "Given that learning of word meanings is often incremental rather than “all or nothing" (p. 21). This underscores the importance of building an environment where students are constantly engaging with and expanding their vocabulary.

 https://www.readingrockets.org/topics/assessment-and-evaluation/articles/classroom-vocabulary-assessment-content-areas 

The following link from a Reading Rockets article explains effective ways to assess vocabulary beyond simple definitions by focusing on depth of word knowledge and contextual use. It suggests methods such as self-assessments, word association tasks, and morphological awareness exercises to measure understanding. Teachers can also assess vocabulary through writing assignments, discussions, and performance-based tasks that require students to use words in context. These strategies provide a more accurate picture of students' vocabulary knowledge and help ensure they can apply new words meaningfully.