I need 2 paragraphs for that question: What does it mean to know a word?

Word meaning: Knowing a word entails understanding it when it is written and/or spoken by. others in formal contexts. Native speakers do this readily without asking for clarification, but. second language learners need to acquire this tacit knowledge of vocabulary.

Comprehension improves when you know what the words mean. Since comprehension is the ultimate goal of reading, you cannot overestimate the importance of vocabulary development. Words are the currency of communication. A robust vocabulary improves all areas of communication - listening, speaking, reading and writing.