I know that “that is” comes from Latin “id est”, short “i.e.” and means “in other words”.
I would like to know whether there is a French equivalent for this phrase.
I think the closest translation of “that is” would be “c’est-à-dire”, which litterally means “that is to say”. It can be shortened to “c-à-d” or “c.a.d.”
“Autrement dit” and “en d’autres termes” also both exactly mean “in other words”.
à savoir is the French equivalent of Latin's 'id est'
i.e.
is also used in french as is, especially (but not limited) to refering scientific work (mathematical, for instance).