interpolation

(noun) a message (spoken or written) that is introduced or inserted. Synonyms: insertion. Examples: "With the help of his friend's interpolations his story was eventually told." "With many insertions in the margins."

(noun) (mathematics) calculation of the value of a function between the values already known.

(noun) the action of interjecting or interposing an action or remark that interrupts. Synonyms: interjection, interposition, interpellation.