1
Keratin
The protein your hair is made of.
Every strand is mostly keratin, a tough protein also found in your nails. In coily hair the keratin is packed into a flat, ribbon-like strand instead of a round one, and that flat shape is what makes the hair coil. When keratin breaks down from heat or harsh chemicals, the strand weakens, which is why protein treatments help repair it.
2
Porosity
How easily your hair absorbs water, and how quickly it loses it.
Low porosity hair has a tight cuticle that resists water, so products sit on top and it takes a while to get fully wet. High porosity hair has a raised or damaged cuticle that absorbs quickly but dries quickly as well. Most coily hair sits somewhere in the middle. Warm water and humectants help low porosity hair absorb; heavier butters and sealing help high porosity hair hold on.
3
Density
How many strands you have, not how thick each one is.
Density is strands per square inch of scalp. High density means a full, thick head of hair even if each strand is fine. Density is separate from your coil pattern, and it decides things like how much product you need and how long styles take. Higher density requires more product and more time.
4
Shrinkage
The tendency of coily hair to spring back, concealing up to three quarters of its length.
Shrinkage happens because each coil is a spring. Wet it, stretch it, and it looks long; let it dry, and it springs back up. It is not damage and it is not a flaw. Strong shrinkage is actually a sign of healthy elasticity. If you want length to show, stretch styles like twist-outs and braid-outs do the job without heat.
5
Heat damage
When high heat permanently breaks the bonds that hold your coil.
Flat irons and hot combs work by breaking hydrogen bonds, which is temporary. But too much heat, too often, breaks the stronger keratin bonds underneath, and those do not come back. The sign is straight, limp sections that remain straight even after washing. The only remedy is to cut them off, which is why heat protectant and low, occasional heat matter.
6
Breakage vs. shedding
Shedding is natural. Breakage is a sign that the hair needs care.
Everyone sheds 50 to 100 hairs a day, and on wash day it can look like a lot, especially with shrinkage hiding it all week. That is normal. Breakage is different: short snapped pieces, often with no bulb at the end. Breakage means the hair is dry, weak, or over-manipulated, and it asks for moisture, gentleness, and trims, not panic.
7
Moisture-protein balance
Your hair needs both water and strength, in the right ratio.
Too little protein and hair feels mushy, stretches too far, and snaps. Too much protein and it feels stiff, dry, and brittle. Coily hair usually thirsts for moisture first, with regular light protein to keep it strong. If your hair suddenly stops responding to your routine, this balance is the first place to look.
8
The cuticle
The shingle-like outer layer of each strand.
Picture roof shingles lying flat. When the cuticle lies flat, hair looks shiny, holds moisture, and resists tangles. When it lifts, from dryness, friction, or harsh products, hair looks dull, frizzes, and tangles. Almost everything in haircare, from pH-balanced products to satin pillowcases, is about keeping those shingles lying down.
9
Protective styling
Styles that tuck your ends away so they can rest.
Braids, twists, and locs keep the oldest, most fragile part of your hair, the ends, tucked away from friction, weather, and daily handling. Length is retained by keeping what grows. Hair grows at its own pace; the ends are what you can save. The condition is that the style itself must be gentle. Too-tight braids damage more than they protect.