noun
plural -sions
the act of making your thoughts, feelings, etc., known by speech, writing, or some other method :the act of expressing something [noncount]
[count] :a word or phrase
People say excuse/pardon/forgive the expression when they are using a word or phrase that might offend or annoy someone.
[count] :the way someone's face looks that shows emotions and feelings
[noncount] :a way of doing something (such as speaking or singing) that shows emotions and feelings
[count] mathematics :a symbol or a combination of symbols and signs representing a quantity or process