Curl pattern is determined by how evenly the two halves of a hair strand grow. When fiber grows faster on one side and not another, a spiral is formed along the cuticle of the hair strand. Depending on genetics, this can be straight, wavy (C-shaped), curly (S-shaped), or kinky/extremely curly (very tight S shape or Z shape).
There is an easy alphanumeric system to identify your type of curl. The numbers 1 through 4 represent the amount of turns formed by hair strands. Number 1 is straight; 4 is extremely curly/kinky.
The lowercase letters a through c determine the texture and sub-group of each curl type. The letter a denotes a finer hair texture; b is medium; c, thick.
Just because hair is extremely curly, does not mean that each individual strand is thick. In fact, most people with type-4 curls fall into subgroups a and b, the subcategories of fine or medium hair.
It often surprises people to learn that extremely curly hair is much more fragile than wavy or straight hair, as each acrobatic bend in the hair is a weak point. This is in direct contrast to coarse hair, which is resilient and does not have finer segments.
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