This is a contracted form of τοῦτ᾽ ἔστι, literally 'this is,' used as an explanatory or clarifying formula meaning 'that is (to say)' or 'in other words.' It functioned like modern parenthetical clarifications, allowing writers to restate something in different terms or provide additional specificity. New Testament authors used it when defining terms, explaining concepts, or ensuring readers understood the significance of what was just stated. The contraction into a single word made it a standard discourse marker, smoothly introducing explanatory material without disrupting narrative or argument flow. It helped bridge the gap between technical or foreign terms and Greek readers' understanding.