Not defined line number

Not defined line number

"Failed to update function
Variable 'ticketID' is not defined Line Number : 3"

Above shows when I enter below. Can you help me with this?
  1. deskDomain = "https://desk.zoho.com";
  2. //Replace your zoho desk URL accordingly
  3. jsonString = {"ticketIds":{ticketID}};
  4. deleteTicket = invokeurl
  5. [
  6. url :deskDomain + "/api/v1/tickets/moveToTrash"
  7. type :POST
  8. parameters:jsonString.toString()
  9. connection: "autodeletetickets"
  10. ];