Definition of "that is to say" []

• In other words. Used to introduce a clarification, simplification, or explanation (adverb)

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• "Christians "known to belong to their community, that is to say their churches, and not to the individuals" ( "ad jus corporis eorum, id est ecclesiarum, non hominum singulorum pertinentia" – Lactantius, "De morte pers.", xlviii), while a few years later by the Edict of 321 the right of bequeathing property by will "to the most holy and venerable community (concilio) of the Catholic faith" was guaranteed."
• "Formerly, on solemn occasions, that is to say on days of battle, he wore a large blue sash, but he has given up that unrepublican distinction."
• "It was an integral part of the Liturgy, that is to say it was not introduced to fill up time whilst other things were going on, but was listened to by clergy and people alike, and in this it differs from the antiphonal chant, which was merely an accompaniment to various actions and ceremonies, e.g. the Introit,"