Reference
Hair transplant glossary
42 terms used across hair restoration surgery, diagnostics, regenerative therapy and clinic operations — defined the way we use them in our guides. Definitions are written to stand alone; cite them with a link back to this page.
Deep-dive entries
12 core terms have full explanatory pages — definition, how it works in practice, and where to go deeper.
Surgical techniques
- FUE (Follicular Unit Excision / Extraction)
- A hair transplant technique in which follicular units are harvested one by one from the donor area with a small punch, leaving dot scars instead of a linear scar. Extraction, channel creation and implantation are performed as separate steps.Full entry Full guide
- FUT (Follicular Unit Transplantation, “strip”)
- The older harvesting method in which a strip of donor scalp is excised and dissected into follicular units under magnification. It yields large graft numbers in one pass but leaves a linear donor scar.Full entry
- DHI (Direct Hair Implantation)
- A variant of FUE in which extracted grafts are loaded into a Choi implanter pen that creates the recipient channel and places the graft in a single motion, shortening the time grafts spend outside the body.Full entry Full guide
- Sapphire FUE
- FUE performed with recipient channels opened by sapphire-tipped blades rather than steel. The harder, smoother blade edge is marketed as producing finer channels; surgeon skill remains the dominant outcome variable.Full entry Full guide
- Choi implanter pen
- A spring-loaded pen with a hollow needle that holds a single graft and implants it while creating the channel. Available in multiple needle diameters matched to graft size; the defining instrument of DHI.Full entry Full guide
- Channel creation (site making)
- The step of opening recipient-site incisions that determine the angle, direction and depth of each implanted graft. Channel geometry is the main surgical control over how natural the final result looks.
- Tumescence
- Injection of dilute saline–adrenaline solution into the scalp to firm the tissue, reduce bleeding and lift follicles away from deeper structures during extraction or channel creation.
- Hairline design
- Planning the shape, height and irregularity of the reconstructed frontal hairline before surgery. Good design follows facial proportions, age-appropriate recession and soft single-hair transition zones.Full entry Full guide
Grafts & donor area
- Follicular unit
- The natural anatomical bundle in which scalp hair grows — one to four terminal hairs with shared supporting structures. Modern transplantation moves intact follicular units rather than individual hairs.
- Graft
- The transplantable unit of tissue containing one follicular unit. Graft counts, not hair counts, are the standard unit of surgical planning and pricing; one graft typically carries 1–4 hairs.
- Donor area
- The band of occipital and temporal scalp whose follicles are genetically resistant to androgenetic hair loss, making it the source of transplantable grafts.Full entry
- Safe donor zone
- The portion of the donor area least likely to miniaturise over a lifetime. Harvesting outside it risks transplanted hair thinning later along with native hair.
- Transection
- Cutting or damaging a follicle during extraction or dissection so it cannot survive transplantation. The transection rate is a core quality metric of a harvesting team.
- Graft survival rate
- The percentage of implanted grafts that produce growing hair after roughly 12 months. Handling discipline, hydration, out-of-body time and implantation trauma are its main determinants.Full entry Full guide
- Out-of-body time
- The interval between graft extraction and implantation. Keeping it short — and keeping grafts cool and hydrated meanwhile — protects graft viability.
- Holding solution
- The chilled liquid in which extracted grafts are stored while awaiting implantation — commonly saline, Ringer’s lactate, or specialised preservation media.Full guide
- Overharvesting (donor depletion)
- Extracting so many grafts that the donor area looks visibly thinned or moth-eaten. It is irreversible, and avoiding it is a marker of ethical surgical planning.
- Density (grafts/cm²)
- The number of grafts implanted per square centimetre of recipient scalp. Natural-looking results balance density against blood supply limits and total donor reserves.
Medical & diagnostic
- Androgenetic alopecia (AGA)
- Hereditary, hormone-mediated hair loss — the common “male pattern” and “female pattern” baldness. It is progressive, driven by follicular sensitivity to DHT, and is the main indication for hair transplantation.Full entry
- DHT (dihydrotestosterone)
- The androgen chiefly responsible for follicular miniaturisation in genetically susceptible scalp regions. Finasteride works by inhibiting the enzyme that converts testosterone to DHT.
- Miniaturisation
- The progressive shrinking of follicles under androgen influence, producing shorter, finer hairs each cycle until growth stops. Its extent, seen on trichoscopy, guides prognosis and treatment.
- Norwood scale
- The standard classification of male pattern hair loss, stages I–VII, describing progressive recession and vertex thinning. Used to stage patients, plan grafts and communicate prognosis.Full entry
- Ludwig scale
- The standard classification of female pattern hair loss, grades I–III, describing diffuse thinning over the crown with a preserved frontal hairline.
- Trichoscopy
- Dermoscopic examination of the scalp and hair shafts. It quantifies miniaturisation, distinguishes androgenetic alopecia from other alopecias, and documents treatment response.
- Hair growth cycle (anagen, catagen, telogen)
- The follicle’s repeating phases: anagen (active growth, years), catagen (brief involution), telogen (rest, months) ending in shedding. Most therapies aim to prolong anagen or re-enter it.
- Telogen effluvium
- Diffuse temporary shedding triggered when stress, illness, surgery or medication pushes many follicles into telogen simultaneously. It is self-limiting and must be distinguished from pattern loss before any transplant decision.
- Shock loss
- Temporary shedding of native (and occasionally transplanted) hair in the weeks after surgery, caused by perioperative stress to follicles. Most of it regrows within months.
- Finasteride
- An oral 5α-reductase inhibitor that lowers scalp DHT and slows or partially reverses male androgenetic alopecia. Commonly used to stabilise loss before and after transplantation, under physician supervision.
- Minoxidil
- A topical (or off-label low-dose oral) vasodilator that prolongs anagen and thickens miniaturised hairs in androgenetic alopecia. Effect is maintained only while treatment continues.
PRP & regenerative therapies
- PRP (platelet-rich plasma)
- An autologous concentrate of platelets prepared by centrifuging the patient’s blood, injected into the scalp to support hair growth through platelet-derived growth factors. Used alone or alongside transplantation.Full entry Full guide
- Platelet concentration factor
- How many times more concentrated platelets are in the final PRP than in whole blood. Preparation systems differ widely; the factor is a key variable when comparing protocols and published results.
- Single-spin vs double-spin
- The two centrifugation approaches to PRP preparation. Single-spin is faster with lower concentration; double-spin separates and re-concentrates platelets for higher yields at the cost of time and technique sensitivity.
- Closed vs open PRP system
- Closed systems keep blood in sealed single-use kits throughout processing, minimising contamination risk; open systems use manual pipetting in standard tubes — cheaper, but demanding strict aseptic technique.
- Mesotherapy
- A technique of delivering small intradermal or subcutaneous injections of active compounds — vitamins, minerals, medications — across the scalp. Protocols and evidence vary widely by cocktail and operator.Full entry Full guide
- Microneedling
- Controlled micro-injury of the scalp with fine needles to stimulate wound-healing pathways and enhance topical absorption. Often combined with minoxidil or PRP in androgenetic alopecia.
- Exosomes (investigational)
- Cell-derived signalling vesicles marketed for hair regrowth. Regulatory status and clinical evidence are still evolving; most jurisdictions have not approved exosome products for alopecia.
Clinic & operations
- Graft calculation
- Estimating the number of grafts needed from the recipient surface area and target density, balanced against donor reserves and future loss progression. The basis of honest surgical quotes.
- Patient coordinator
- The non-clinical team member who guides a patient from enquiry through consultation, scheduling, travel and aftercare follow-up. In international clinics, the role carries much of the patient experience.Full guide
- Hair transplant technician
- The trained team member who performs graft extraction assistance, sorting, counting and loading — and in many clinics, implantation support — under surgeon supervision. Team skill directly moves graft survival.Full guide
- Informed consent
- The documented process of explaining a procedure’s expected outcome, limits, risks and alternatives before the patient agrees. For hair transplants this includes donor scarring, shock loss and the likely need for future sessions.
- SOP (standard operating procedure)
- A written, versioned instruction covering one clinical or operational process — from instrument reprocessing to consultation scripts. SOPs make quality reproducible across staff and sessions.Full guide
- Medical tourism (international patients)
- Patients travelling abroad — prominently to Türkiye — for hair restoration. Running it well requires structured remote consultation, travel logistics, translation and remote aftercare.Full guide
Missing a term you expected? Tell us — the glossary is revised alongside our guides. Definitions are educational and not medical advice.