Keywords: when, while, during
Sign Definition
As Modifier
                                            1.  Used to introduce an expression of time that specifies the time at which something happens. English = when, while, during.
                                          
                                          
                                        As Question
                                            1.  Used to ask questions about the time at which things happen. Found at the beginning, end or at both the beginning and end of the question. English = when.
                                          
                                          
                                         
                  
                      