(n.) A doubling together or folding; a duplication.

Janus ambiguity ambivalence biformity bifurcation bush bushing conduplication conjugation copying crease creasing crimp dichotomy dog-ear double doubleness doublethink doublure dualism duality duplexity duplicate duplication duplicature duplicity echo equivocality facing filler filling flection flexure flounce fold frill gather gemination halving imitation ingemination inlay inlayer insole interlineation irony iteration lapel lappet liner lining packing padding pairing plagiarism plica plication plicature ply polarity quotation reappearance rebirth recurrence redoubling reduplication reecho regurgitation reincarnation reiteration renewal reoccurrence repetition replication reproduction resumption return ruche ruching ruffle stuffing tuck twinning two-facedness twoness wadding wainscot