Comfortable With All the Waves Bar One

There are more waves in the world, than One would think, And the list is continually being added to. There are waves in the water and waves in the air, Waves seen and unseen, Waves that bend and waves that don't, Short waves and long waves, Even shock waves and sound waves. Not long-ago microwaves got added to the list, And we did not always know that radio waves existed, Though we have always known heat waves, And humans have never stopped making waves of their own. Yet it is the wave that signals that it is time to say goodbye, That is the hardest for me to come to terms with.