即是 is a formal conjunction meaning 'namely', 'that is to say', or 'in other words'. It functions to introduce a clarification, definition, or restatement—often used in written Chinese, academic contexts, or precise explanations. The character 即 means 'immediately' or 'precisely', conveying immediacy and equivalence; 是 means 'to be', anchoring the statement as an assertion of identity or equivalence. Together, 即是 emphasizes that what follows is not merely similar but identical in meaning or function to what precedes it.

This phrase is common in definitions, instructions, logical reasoning, and explanatory texts—such as textbooks, official notices, or formal speeches. It is rarely used in casual conversation, where simpler alternatives like 就是 or 也就是 are preferred. 即是 often appears after a noun or clause and before its explanation, helping the reader recognize a definitional relationship rather than mere illustration.