This question is about understanding basic linguistic terms. The correct answer is 'B. Synonym' because it refers to words that have similar or identical meanings. 'A. Prohibit' is a verb that means to forbid, which is unrelated to word meanings. 'C. Antonym' refers to words with opposite meanings, which is the opposite of what the question asks. 'D. Homophone' refers to words that sound the same but have different meanings and spellings, which is not about similar meanings.