the repetition of an experiment in order to test the validity of its conclusion; "scientists will not believe an experimental result until they have seen at least one replication"
(law) a pleading made by a plaintiff in reply to the defendant's plea or answer
(genetics) the process whereby DNA makes a copy of itself before cell division
moving from one place to another and back again; "he traveled back and forth between Los Angeles and New York"; "the treetops whipped to and fro in a frightening manner"; "the old man just sat on the porch and rocked back and forth all day"