Stearic acid is the saturated fatty acid

Fatty acid

In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...

 with an 18 carbon chain and has the IUPAC name octadecanoic acid. It is a waxy solid, and its chemical formula is CH₃(CH₂)₁₆CO₂H. Its name comes from the Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 word στέαρ "stéatos", which means tallow

Tallow

Tallow is a rendered form of beef or mutton fat, processed from suet. It is solid at room temperature. Unlike suet, tallow can be stored for extended periods without the need for refrigeration to prevent decomposition, provided it is kept in an airtight container to prevent oxidation.In industry,...

. The salts and ester

Ester

Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

s of stearic acid are called stearates. Stearic acid is noteworthy as the most common saturated fatty acid, another common one being the C16 compound palmitic acid

Palmitic acid

Palmitic acid, or hexadecanoic acid in IUPAC nomenclature, is one of the most common saturated fatty acids found in animals and plants. Its molecular formula is CH314CO2H. As its name indicates, it is a major component of the oil from palm trees . Palmitate is a term for the salts and esters of...

.
It occurs in many animal and vegetable fats and oils, but it is more abundant in animal fat (up to 30%) than vegetable fat (typically <5%).