Hair width (sometimes called texture) refers to the thickness of individual strands of your hair, rather than to how much hair you have on your head. Knowing your hair width, along with your unique curl pattern, is important since it can affect your ability to retain length.
To find your hair width, take piece of your hair from a brush or comb and hold it up to the light. If the hair is very wide and easily visible, then you have coarse hair. If it's so thin that you can hardly see it, you have fine hair. If your hair appears neither thin nor coarse, you have medium width hair.
The strands in coarse hair are very wide in circumference, making them the strongest of all hair textures. As a result, it's easy to maintain length with coarse hair since it's more resistant to damage.
Hair with medium width consists of strands that are strong and elastic, and neither too thin nor too thick. Medium width hair is also somewhat resistant to damage, making it easy to maintain length.
Hair with fine width has a very small circumference and is very delicate and easy to damage. As a result it's often difficult to maintain length with fine hair. Deep conditioning after you wash is a good way to nourish and strengthen fine hair. You'll also want to keep manipulation of your hair to a minimum to avoid unnecessary breakage by reducing your use of combs and brushes and steering clear of elaborate, high-maintenance hairstyles.