The term oil is used to indicate a high viscosity organic liquid
lipophilic (ie miscible with other oils) and hydrophobic (ie immiscible with water).
Originally it referred solely to the olive oil obtained from the pressing of the
fruits of the olive tree. Later this name was extended to all lipids found in the state
liquid at room temperature and also to other liquids that have similar properties but
different composition (e.g. mineral oils).
They are used for food purposes, as fuels, lubricants and in the production of
paints, plastics and other materials. They are also used in religious ceremonies
as a vehicle of purification.

Chemical-physical properties

Oils of biological origin consist mainly of glycerides and secondarily
from other secondary components, such as: free fatty acids, phospholipids, sterols, hydrocarbons,
pigments, waxes and vitamins.
All oils, although they have a different chemical composition, have
some characteristics that unite them, which are:
liquids at room temperature
greasiness
density generally lower than water
generally flammable
insolubility in water.

Classification

Depending on where they are extracted from, oils (also called fatty or lipid oils) can be
divided into: animal oils: they are formed by esters of glycerine and fatty acids of animal origin;
the most common animal oils are oils from aquatic animals, especially oils from cetaceans
and fish oils (e.g. cod liver oil); they are often used in the
realm pharmacological; vegetable oils: generally obtained from the seeds of many plants (eg rapeseed oil),
from the germs of grain kernels or from the pulp of some fruits (olive oil);
they are often used as edible oils, in the field of cosmetics, in oil paint
(in the form of siccative oil) and to a lesser extent as biofuels; they can also be
hydrogenated to make margarine; mineral oils: petroleum and its natural liquid derivatives
hydrocarbon; they are often used as fuel and as lubricants;
essential oils or essences: mixtures of terpenes, often odorous; they are very volatile and come
often used in cosmetics. (source Wikipedia)


(selection 2023)