|ikˈspre sh ən|
noun

1 the process of making known one's thoughts or feelings : his views found expression in his moral sermons | she accepted his expressions of sympathy.
• the conveying of opinions publicly without interference by the government : the right to freedom of expression.
• the look on someone's face that conveys a particular emotion : a sad expression.
• the ability to put an emotion into words : envious beyond expression.
• a word or phrase, esp. an idiomatic one, used to convey an idea : nowhere is the expression “garbage in, garbage out” any truer.
• the style or phrasing of written or spoken words : subtlety of expression.
• the conveying of feeling in the face or voice, in a work of art, or in the performance of a piece of music : eyes empty of expression | their instruments have a rich variety of expression.
• Mathematics a collection of symbols that jointly express a quantity : the expression for the circumference of a circle is 2πr.
• Genetics the appearance in a phenotype of a characteristic or effect attributed to a particular gene.
• (also gene expression) Genetics the process by which possession of a gene leads to the appearance in the phenotype of the corresponding character.