expression

noun

• 1the action of making known one’s thoughts or feelings:the prisoners developed a dialect as an everyday means of expression [count noun]:she accepted his expressions of sympathy
• the conveying of feeling in a work of art or in the performance of a piece of music: the testimony of musicians who worked with him proves that his overwhelming concern was with expression

• 2 [count noun] a look on someone’s face that conveys a particular emotion:a sad expression

• 3 [count noun] a word or phrase, especially an idiomatic one, used to convey an idea:we have an expression, ‘You don’t get owt for nowt.’
• Mathematics a collection of symbols that jointly express a quantity:the expression for the circumference of a circle is 2πr

• 4the production of something by pressing it out:essential oils obtained by distillation or expression

• 5 Genetics the appearance in a phenotype of a characteristic or effect attributed to a particular gene: expression of the TAT gene is restricted to the parenchymal cells