Denim and jean have been around for centuries, and although their reign has been (somewhat) toppled by activewear, they still remain an essential part of the fashion world. But many still find the two terms confusing. Which one is jean and which one is denim?

Jean fabric came from Genoa, Italy and was originally a blended twill of wool and cotton. Jean was very similar to cotton corduroy (also a famous product of Genoa). It was worn by the sailor of Genovese Navy force since they needed a fabric for both wet and dry. In 1800, André Masséna (one of Marshals of the Empire appointed by Napoleon) had his troops placed in the city and ordered supply from Jean-Gabriel Eynard, a Swiss banker who migrated to Genoa to start a business in the city. One of the supplies Eynard furnished the troops was that twill fabric dyed in blue called "bleu de Genes" ("blue from Genoa") and you guessed it, the term "blue jeans" was born.

Meanwhile denim hailed from Nîmes, a city in southern France. Its full name is "serge de Nîmes" or simply "fabric from Nîmes." It began as a blend of wool and silk, making the cloth very durable and sturdy. These characteristics mean the first denim fabrics were difficult to sew, since it required industrial-strength needle. They were also expensive, since wool and silk weren't (and aren't) as abundant as cotton. The original denim was created by the shepherds in the Cévennes mountains (just northwest of Nîmes) since they needed durable clothes to work in.

It was around the 17th century that denim fabric and jeans fabric intersected. Some argue that denim (made of wool and silk) were coarser yet considered of higher quality, more expensive, and more durable sibling, whilst jeans (wool and cotton) were lighter, still durable, and less expensive. Nobody really knows why blue (or more accurately indigo) was used, perhaps because the jean fabric was intended for the Genovese Navy force. Weavers in Nîmes were said to have tried to reproduce jean, but found a different way to do it. Maybe this was the reason why denim fabrics were also dyed indigo.

Jean became an essential textile for working-class people in Northern Italy so much so that a painter nicknamed The Master of the Blue Jeans (perhaps a student of Caravaggio) created ten paintings depicting scenes with lower-class and working-class people wearing blue fabric. It was most likely Genovese blue jean because it was cheaper than the French denim. Shown here is one of the paintings called A Frugal Meal.

Cut to the modern US fashion history, both denim and jeans had been constructed using 100% cotton, and the first name that comes to mind when we talk about denim is Levi Strauss, and for a good reason.

Strauss (along with Jacob W. Davis) was credited to have given birth to denim and jeans.

In 1851, Strauss migrated from Germany to New York to join his older brother who owned a dry-goods store. He then heard about the San Francisco Gold Rush and moved there two years later to start a West Coast branch of the business.

A few hundred miles away in Reno, Nevada, Jacob W. Davis, a Russian-American tailor, was making heavy duty textiles such as tents, horse, blankets, and wagon covers made from cotton denim supplied by Strauss.

One day, a customer asked Davis to make a pair of work pants for her woodcutter husband, so Davis created a pair of pants using heavy-duty cotton duck (a type of woven pattern different from denim and jeans). This became a success and by 1871, instead of cotton duck, he used Levi's cotton blue denim for the pants which featured seams on the fly and pockets reinforced with rivets. In fact, the demand for the pants were so high (thanks to miners and workers wearing them during the Gold Rush) that Strauss and Davis patented the pants (along with the copper-rivet reinforcements and orange double stitching). The two men became business partners. Davis ran the manufacturing division of Levi Strauss & Co. whilst Strauss continued to experiment with different fabric variations and styles. The styles were given numbers, including the popular Levi 501s.

For reasons unknown, although the fabric that Strauss and Davis used was denim, the style (of the pants later became known as jeans.

And the confusion began.

Some have argued that "denim" refers to the fabric whilst "jeans" refers to the style of pants, and by extension, all of jean pants are made of denim, but not all denim is jeans. However, now we know that both denim and jean are indeed fabric. Both denim and jeans are wrap-woven twill.

In the past, denim was constructed using wool and silk, whilst jeans used wool and cotton. Nowadays, they're both mostly 100% cotton. The difference is in the dye, or rather, the time of the dye.

True denim uses two yarns: one color (most likely blue), the other white, meaning it has already been colored before being woven.

True jeans fabric, on the other hand, whilst also uses two yarns, is dyed after the fabric has been woven.

The only sure way to find out if your piece of clothing is denim or jeans is to see both sides. Since denim is warp woven using two yarns of different colors, one surface will feature one color whilst the other will have another. Because jean is dyed after it's woven, both surfaces have almost the same color.

Now that you know which one is which, it shouldn't destroy your love for denim and or jeans. In fact, these two fabrics are so ubiquitous and essential at the same time that they are so versatile. Make them your own by adding embellishments like Swarovskis or patches. Wear them even when they're ripped because shredded jeans show character. Wash them over and over again until they're faded because there's history in them. Wear them on top of your athleisure or activewear or dresses to complete a casual look.

One thing for sure, don't exercise in jeans. We have activewear for that.