Expression: 'That is to say'

[Tom]

Hi

Could you please tell me if the expression that is to say common both in written and spoken English? What does it really mean? Could you please use it in a sentence for me? Is it synonymous with that said?

Tom

[Conchita]

That is to say means 'in other words', 'or more exactly', 'or to put it another way' or 'I mean'.

We're only human -- that is to say, we don't always think with our head.

That said has a different meaning -- it is used in the sense of 'having said that' or 'however'.

He can be quite moody at times. That said, he is very generous and helpful.

[Tamara]

Can I consider that in writing i.e. is an acceptable equivalent for That is to say?
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It’s impossible to learn swimming without entering the water…

[Conchita]

[Tom]

[Conchita]

Oh, dear! Sorry, Tom! Don't you hate it when people seem to be speaking in some kind of code?

'i.e.' stands for the Latin 'id est', which means 'that is (to say)' or 'in other words', as Tamara rightly assumed.