Alchemy (Japanese 錬金術) is an early form of chemistry that was used to perfect and formulate new chemical compounds through combining materials.

How Long Has Alchemy Been Around In The World?[]
It is unknown how long alchemy has been around in the Monster Hunter world, but is relatively common today. It is also unknown where it originated from.
What Forms Of Alchemy Have Been Seen In The World?[]
For the general public, alchemy is viewed as a pseudoscience that can't be perfected by normal people, however, it is normal for hunters to use alchemy on a daily basis. Hunters are known to use alchemy in order to combine items and create certain materials to further perfect their hunting skills. Though a lot of hunters use alchemy, not all of them have perfected it. On some occasions, hunters mistakenly make worthless garbage that no one wants. In order to get the best results out of alchemy, hunters are known to use a set of books, known as the Books of Combos, or even use special armor skills to further their alchemy. Recently, hunters have invented a new Hunting Style that specializes in using alchemy to make new items that can be used to help them during a hunt.
In some places, such as Cathar and Kokoto Village, are melders that combine use certain items like Frenzy Crystals to meld charms together, in order to create new ones. The same also goes for some shopkeepers.