Definition: A telephone is a device that allows you to talk to someone who is far away. It works by changing your voice into electrical signals, sending those signals through wires or the air, and then changing them back into sound for the other person to hear.
As a noun: You can use "telephone" when you are talking about the device itself.
As a verb: You can use "telephone" when you mean to call someone.
In more advanced contexts, "telephone" can refer to various forms of communication, including mobile phones and VoIP (Voice over Internet Protocol) services.
In some contexts, "telephone" can also refer to the act of making a call, not just the device. For example, "He is on the telephone" can mean he is currently talking on the phone.
"Call up": To make a phone call to someone.
"Get through": To successfully reach someone by telephone.