4c is a popular way of describing Afro hair that has small tight curls. 4C stands for the curl type. In the 90's Oprah's then hairdresser came out with a hair book, which detailed a Hair Typing System. Andre Walker created a number-letter system in order to classify all hair types. The chart goes from 1 to 4. One being the straightest hair and 4 being the tightest curl.
View his complete hair classification system HERE
He classifies type 4 hair as kinky, coily. A letter is added to the number to distinguish curl shape and size. Originally he had two classifications for type 4 hair.
Type 4A hair is full of tight coils. It has an "S" pattern when stretched.
Type 4B hair has a less defined pattern of curls and looks more like a "Z" pattern. This is because the hair bends with very sharp angels.
CURL TYPE 4C
Type 4C hair is not, a part of the Andre Walker Hair Typing System. Andre advises that if you cannot see a defined curl pattern, then you are most likely type 4B. The natural hair community didn't find this sufficient. So type 4c was added, by those who feel they do not fit into category 4A or 4B.
Most feel they are 4C because they do not have perfect coil formation. Because they cannot easily apply some gel and get glossy spirals, many are perplexed. The problem is that they are working with dehydrated hair. Afro hair that is chronically losing moisture will not have good curl formation. Correct your hair hydration before doing a wet set aka wash and go. (4C HAIR IS NOT DRY BY DEFAULT)
If your hair has 3 or more of these characteristics, you are Curl type 4C
Afro hair that at first glance appears to have no curl, because your strands do not clump naturally.
Not glossy but opaque, dull in appearance.
Shrinks 75% or more
Curls are very tight and small.
It coils up and separates, giving the appearance of small knots, most call naps. But those are curls.
Very springy, spongy
Forms small wave crinkles when smoothed down.