that is to say
fixed phrase.you use this when you want to explain something more clearly or give more detail about what you just said.
fixed phrase.a parenthetical phrase used to introduce a clarification, a more precise restatement, or a specific explanation of a preceding statement.
“He is a polyglot; that is to say, he speaks many languages.”
“The company is restructuring, that is to say, some departments will be merged to save costs.”
“The results were statistically insignificant; that is to say, the observed variations could easily have occurred by chance alone.”
usually set off by commas or a semicolon to separate the clarification from the main clause.
teach this as a more formal alternative to 'in other words' or 'I mean'; it is particularly useful for academic writing and formal presentations.