Which term best describes words not common in everyday language but used in specific domains?

• A. Tier 3 words
• B. Core vocabulary
• C. Slang words
• D. Onomatopoeic words

Answer: (A)

Words not common in everyday language but used in specific domains are Tier 3 words. These are specialized terms tied to a subject such as science, history, or mathematics. They show up in textbooks, lectures, and exams, yet rarely in casual conversation. Because they’re domain-specific, they require direct instruction and practice in the context where they appear; for example, terms like photosynthesis, isotope, or metamorphosis only become meaningful when students are exploring those topics. This helps explain why such words are distinct from everyday vocabulary and from other types of words. Slang words are informal and casual; onomatopoeic words imitate sounds; and core vocabulary refers to everyday words used across many contexts, not tied to a particular domain.