Fats consist of a wide collection of compounds that are usually soluble in organic solvents and mainly insoluble in water. Chemically, fats are normally triesters of glycerol and fatty acids. Fats may be either solid or liquid at normal room temperature, depending on their structure and composition. Though the words "oils", "fats", and "lipids" are all used to refer to fats, "oils" is usually used to refer to fats that are liquids at usual room temperature, while "fats" is usually used to refer to fats that are solids at regular room temperature. "Lipids" is used to refer to both liquid and solid fats, the length of with other related substances. The word "oil" is used for any substance that does not combine with water and has a greasy feel, such as petroleum (or crude oil) and heating oil, in spite of of its chemical structure.
