The word **对应** (duìyìng) is a compound formed by combining two distinct characters, each contributing to its overall meaning. The first character, **对** (duì), carries meanings such as "to face," "opposite," or "mutual," establishing a sense of bilateral orientation. The second character, **应** (yìng), means "to respond," "to answer," or "to correspond." When combined, they create a verb or noun that conceptually describes a state where one thing **faces and directly correlates or matches to another**, forming a paired, reciprocal relationship. This formation follows a common Chinese grammatical pattern where two verbs or conceptual characters are placed together to express a more complex, abstract idea—in this case, a one-to-one correspondence, mapping, or equivalence, such as between words in translation, items in a list, or inputs and outputs in a function.