Denim (which gets its name from the French for "from Nîmes" (de Nîmes)) is a rugged cotton twill textile, in which the weft passes under two (twi- "double") or more warp threads. This twill weaving produces the familiar diagonal ribbing of the fabric, which distinguishes denim from cotton duck.
It is characteristic of any indigo denim that only the warp threads are dyed, whereas the weft threads remain plain white. As a result of the warp-faced twill weaving, one side of the fabric shows the blue warp threads, the other side shows the white weft threads. This is why jeans are white on the inside and what makes denim's fading characteristics unique compared to every[dubious ] other fabric.
The word 'denim' comes from the name of a sturdy fabric called serge, originally made in Nîmes, France, by the André family. Originally called Serge de Nîmes, the name was soon shortened to denim.. Denim has been used in America since the late 18th century.
Denim was traditionally colored blue with indigo dye to make blue "jeans", though "jean" then denoted a different, lighter cotton textile; the contemporary use of jean comes from the French word for Genoa, Italy (Gênes), where the first denim trousers were made.
Worldwide market 
In 2007, the worldwide denim market equalled USD 51.6 billion, with demand growing by 5% and supply growing by 8% annually.
Over 50% of denim is produced in Asia, specifically China, India, and Bangladesh. The following table shows where the world's denim mills are located.Region No. of Denim Mills
Asia (China) 297
Asia (other countries) 104
North America 9
Latin America 46
Total Denim Mills (World-wide) 513
Dry denim 
Dry or raw denim, as opposed to washed denim, is a denim fabric that is not washed after being dyed during its production. Over time, denim will generally fade, which is often considered desirable. During the process of wear, it is typical to see fading on areas that generally receive the most stress, which includes the upper thighs (whiskers), the ankles (stacks) and behind the knees (honey combs).
After being crafted into an article of clothing, most denim is washed to make it softer and to reduce or eliminate shrinkage, which could cause an item to not fit after the owner washes it. In addition to being washed, non-dry denim is sometimes artificially "distressed" to produce a worn look.
Much of the appeal of factory distressed denim is that it looks similar to dry denim that has, with time, faded. With dry denim, however, such fading is affected by the body of the person who wears the jeans and the activities of his/her daily life. This creates what many enthusiasts feel to be a more natural, unique look than distressed denim.
To facilitate the natural distressing process, some wearers of dry denim will often abstain from washing their jeans for more than six months, though it is not a necessity for fading.
Selvedge denim 
Selvedge denim (alternative spelling: selvage denim) is a type of denim which forms a clean natural edge that does not unravel. It is commonly presented in the unwashed or raw state. Typically, the selvedge edges will be located along the out-seam of the trousers, making it visible when cuffs are worn.
The word "selvedge" comes from the phrase "self-edge", the natural edge of a roll of fabric. As applied to denim, it means that which is made on old-style shuttle looms. These looms weave fabric with one continuous cross thread (the weft) that is passed back and forth all the way down the length of the bolt. As the weft loops back into the edge of the denim it creates this “self-edge” or selvedge. Selvedge is desirable because the edge cannot fray like denim made on a projectile loom that has separate wefts, which leave an open edge that must be stitched. This advantage is only realized on one edge of the fabric, however, as the fabric has to be cut to shape and anywhere it is cut the self-edge is lost.
Shuttle looms weave a narrower piece of fabric, and thus a longer piece of fabric is required to make a pair of jeans (approximately 3 yards). To maximize yield, traditional jean makers use the fabric all the way to the selvedge edge. When the cuff is turned up, the two selvedge edges (where the denim is sewn together) can be seen. The selvedge edge is usually woven with a coloured stripe: green, white, brown, yellow, and (most commonly) red. Fabric mills used these colours to differentiate between fabrics. Contrary to popular belief, the stripe is not sewn in finishing the product, but woven into the fabric itself.
Most selvedge jeans today are dyed with synthetic indigo, but natural indigo dye is available in some denim labels. Though they are supposed to have the same chemical make-up, there are more impurities in the natural indigo dye. Loop dying machines feed a rope of cotton yarn through vats of indigo dye and then back out. The dye is allowed to oxidize before the next dip. Multiple dips create a dark indigo blue.
In response to increased demand for jeans in the 1950s, American denim manufacturers replaced the old shuttle style looms with modern projectile looms. The new looms produced fabric faster and wider (60 inches or wider). Synthetic dying techniques along with post-dye treatments were introduced to control shrink and twist.
Patterns of fading 
Fades caused by prolonged periods of wear, without washing, have become the main allure for raw denim. The fading patterns are a way of personalizing the garment for each customer. These fades are categorized by certain names:
• Whiskers – Faded streaks that surround the crotch area of the denim.
• Combs – Also known, as “honey combs” are the streaks of faded lines that are found behind the knee.
• Stacks – Produced by having the inseam of the denim hemmed a few inches longer than actual leg length. The extra fabric stacks on top of the shoe causing a fade to form around the ankle to calf area of the denim.
• Train Tracks – appears on the outseams of the denim. This fade showcases the selvedge by forming two sets of fades that resemble train tracks.
Stretch denim 
Stretch denim usually incorporates an elastic component (such as elastane) into the fabric to allow a degree of give in garments. Only a small percentage is required within the fabric (approximately 3%) to allow a significant stretch capacity of around 15 percent.
Color denim 
Denim fabric dyeing is divided into two categories; indigo dyeing and sulphur dyeing. Indigo dyeing produces traditional blue colours or shades similar to blue colours. Sulphur dyeing (also called colour denim) is used to create speciality black colours and other colours like pink, grey, rust, mustard, green, and also improve the quality.