"that is" - expression at the and a sentence?

[micky]

good teachers

i have seen the expression "that is" at the end of some sentences. what is the intended meaning?

many thanks

micky

[Yankee]

Hi Micky

It hard to be sure what some things mean in English... unless you ask questions at esl-test.net, that is.

"That is" at the end of a sentence is a short form of "that is to say". This points out a clarification of something previously said. (In my sentence above, "unless you ask questions at esl-test.net" is a clarification of the first half of the sentence.)

"That is" can come before the clarification or after it, and it is separated from the clarification with a comma.

Amy