Hair loss glossary should make the subject easier, not heavier. In plain English, the goal is to define the words people keep seeing across the site so they can understand articles, hubs, and diagnosis pages without feeling lost in medical language.
That matters because many hair-loss terms sound more complicated than they really are. A good glossary should translate the vocabulary into plain English while still keeping the definitions medically accurate enough to be useful.
Medical note: This glossary is for general education and does not replace diagnosis. If a term sounds relevant to your situation but the pattern itself is unclear, start with How Hair Loss Is Diagnosed and When to See a Doctor.
Quick navigation
Start here first
Use this glossary when a word in an article, hub, or diagnosis page is unclear. If the term is familiar but the pattern itself is still confusing, start with the broad map first, then move into the page that matches the main clue.
If you need the broad map first
- Start Here gives the simplest entry point for new readers.
- Hair Loss (Complete Guide) explains how the main pathways fit together.
- Types of Hair Loss helps separate shedding, pattern thinning, patchy loss, scarring alopecia, and breakage.
- Patient Education keeps the practical plain-English guides in one place.
If the term points to a visible pattern
- If the word is about shedding, snapped hairs, regrowth, or density changes, compare Shedding vs Breakage, Hair Shedding Hub, and Hair Regrowth & Recovery Hub.
- If the word describes a visible pattern such as crown thinning, wide part, hairline loss, visible scalp, or lower density, use Visible Thinning: Causes, Clues & Next Steps.
- If the word involves itch, scale, pain, pustules, crusting, or inflammation, use Scalp Symptoms & Hair Loss: Causes & Next Steps.
- If the word relates to beard, brows, lashes, legs, underarm/pubic hair, or several body-hair sites, use Body Hair Loss: Causes, Clues & Next Steps.
If the term points to diagnosis, testing, or treatment
- For diagnostic language such as biopsy, trichoscopy, follicular openings, or pattern clues, use How Hair Loss Is Diagnosed.
- For ferritin, thyroid, nutrient, hormone, or lab-related terms, use Blood Tests & Workup and Lab-Linked Hair Loss Hub.
- For treatment words such as minoxidil, finasteride, response, switching, side effects, or maintenance, use Treatment Overview.
A
Alopecia
The general medical term for hair loss.
Alopecia areata
An autoimmune condition that causes hair loss, often in patches, though it can affect other patterns and body sites too.
Androgenetic alopecia
The medical term for pattern hair loss. It is the most common form of hair loss and can affect both men and women.
Anagen effluvium
A form of hair shedding that happens when hairs in the growth phase are disrupted, often more abruptly than telogen effluvium.
B
Breakage
Hair shaft snapping rather than whole hairs shedding from the root. Breakage can mimic thinning but is not the same as root-level shedding.
Biopsy (scalp biopsy)
A small sample of scalp skin examined under the microscope to help clarify certain diagnoses, especially when inflammation or scarring is a concern.
C
Cicatricial alopecia
Another term for scarring alopecia.
Club hair
A resting telogen hair with the typical bulb-shaped root that is often seen in telogen shedding.
Chronic telogen effluvium
A longer-lasting shedding disorder in which excessive shedding continues or fluctuates beyond the expected short-term course.
D
Diffuse alopecia
Hair loss spread more generally across the scalp rather than confined to one sharply defined spot.
Diffuse shedding
A broad pattern of hair fall affecting the scalp overall, often discussed in telogen effluvium and some overlap conditions.
E
Effluvium
In dermatology, a term used for diffuse hair loss or shedding of different causes.
F
Follicle (hair follicle)
The structure in the skin that produces the hair.
Follicular openings
The small visible openings on the scalp where hairs emerge. Their presence or loss can help clinicians separate some non-scarring patterns from scarring ones.
Frontal fibrosing alopecia (FFA)
A type of scarring alopecia that often affects the frontal hairline and temples, sometimes with eyebrow loss.
M
Miniaturization
A process in which hairs become progressively finer, shorter, and less visible, often discussed in pattern hair loss.
N
Non-scarring alopecia
Hair loss in which follicles are preserved, so regrowth may still be possible depending on the cause.
P
Pattern hair loss
The plain-English term commonly used for androgenetic alopecia.
Patchy hair loss
Hair loss that appears in distinct spots or patches rather than as diffuse thinning.
R
Regrowth
New visible hair growth after a shedding episode, treatment response, or recovery phase. Regrowth may begin before density fully catches up.
S
Scarring alopecia
Hair loss in which follicles can be damaged or destroyed and replaced by scar tissue. This category usually needs faster evaluation than ordinary cosmetic thinning.
Shaft
The visible strand of hair above the skin surface.
T
Telogen
The resting phase of the hair cycle.
Telogen effluvium
A common cause of temporary hair loss due to excessive shedding of resting telogen hairs, often after a trigger or shock to the system.
Terminal hair
The thicker, longer, more pigmented hair that normally makes up scalp hair density.
Traction alopecia
Hair loss caused by repeated tension from hairstyles or grooming practices that pull on the hair.
Trichotillomania
A condition in which a person repeatedly pulls out their hair.
Trichoscopy
A close-up scalp and hair examination technique that helps clinicians assess hair-loss patterns and clues.
V
Vellus hair
Short, fine, lightly pigmented hair. In some hair-loss settings, a shift toward finer vellus-like hairs can be part of the clinical picture.
Related on this site
Start Here • Hair Loss (Complete Guide) • Types of Hair Loss • Medical Classification • How Hair Loss Is Diagnosed • Blood Tests & Workup • Treatment Overview • Hair Regrowth & Recovery Hub • Patient Education • Hair Loss FAQ • Common Myths • When to See a Doctor • Shedding vs Breakage (Practical).
References (trusted medical sources)
- DermNet NZ: Hair Loss
- DermNet NZ: Telogen Effluvium
- DermNet NZ: Alopecia Areata
- DermNet NZ: Diffuse Alopecia
- DermNet NZ: Glossary
- American Academy of Dermatology: Hair Loss — Diagnosis and Treatment
- American Academy of Dermatology: Alopecia Areata
Last updated: April 27, 2026.