Although the two fatty acids have the same number of carbon atoms, they have different three-dimensional configurations; oleic acid has a slight bend near the middle. As a result, a pure sample of:
oleic acid would be more liquid than a pure sample of stearic acid.
stearic acid would be classified as an unsaturated fatty acid.
you would be more likely to find stearic acid in the form of an oil than in the form of a fat.
oleic acid would be classified a saturated fatty acid.

Fatty acids are primarily composed of carbon and hydrogen atoms. They are carboxylic acid with long aliphatic chain. They maybe saturated(without double bond) or unsaturated(with double bond). On the basis of unsaturation they maybe classified as:

•monounsaturated or

•polyunsaturated

Stearic acid is a long saturated fatty acid. They are made up of 18 carbon chain,with molecular formula C17H35COOH. Also known as octadecanoic acid.They are mostly solid at room temperature.

Oleic acid contains one double bond at 9th carbon thus it is a monounsaturated fatty acids. C18H34O2, cis-9-octadecenoic acid,is mostly liquid at room temperature.They are naturally found in various animals and vegetable fats and oils.