Sutures are sterile threads used to approximate wound edges, providing tensile strength during healing phases. Absorbable types include catgut (natural, enzymatically degraded 7-10 days), Vicryl (polyglactin braided, 90% strength at 2 weeks, hydrolyzed 56-70 days), Monocryl (poliglecaprone monofilament, smooth subcuticular 90-120 days), PDS (polydioxanone, slow absorption 6 months for fascia). Non-absorbable encompass Prolene (polypropylene monofilament, inert permanent vascular/skin), Nylon (high memory skin closure), silk (braided handling but reactive). Sizes follow USP (11-0 ophthalmic fine to #7 heavy orthopedic); techniques: simple interrupted (versatile), mattress (eversion), subcuticular (cosmetic). Needle types: taper (GI), cutting (skin), reverse cutting (tendons).