Phrasal Verb: Come on

Meaning: Encouragement

Example: COME ON; don't give up now when you're so close to finishing.

Meaning: Start an illness

Example: I've got a bit of a headache. I hope it doesn't mean I've got flu COMING ON.

Meaning: Start functioning (machines, etc)

Example: The central heating COMES ON automatically an hour before I have to get up.