The word 'Communication' comes from Latin term "communicare"
which actually means "to share". defining communication is difficult, some may define communication as an action that consists of sending or giving or transmitting information(knowledge) form one person to another person. you may found several hundred definition of communication on Internet, everyone can define communication as they want. if you ask to technical(engineer) people they will define in term on technology, if artist they will define in term of art, color etc , in short, no particular definition is available for communication.
On Wikipedia, i found this definition which easy to understand.
"Communication is the activity of conveying information through the exchange of thoughts, messages, or information, as by speech, visuals, signals, writing, or behavior."
OR
"Exchange of meaningful information between two or more living species through a medium."
