By now you must be wondering why I have added a very curious parameter to the definition of Exoplanetology, which is "the search for life on other worlds". What does "Life" have to do with Exoplanets? Should we just let Exoplanetology simply be the study of Exoplanets?
My short answer is simply because Life is fun! But we may in fact leave it plain and simple as the pure science of exoplanets. But I'm afraid that definition will be temporary. In due time, life will ultimately be detected on other worlds. And those who are familiar with James Lovelock's Gaia Hypothesis knows that a planet is never the same once Life takes hold of it. It becomes a planet-life symbiosis. The planet becomes a living organism.
Life ultimately alters the make-up of planets, while on the other hand the undulations of the surface of the planet (earthquakes, volcanic activities, tectonics, etc) affects the course of life's evolution. The metabolisms of life changes the "atmosphere" of planets, vise-versa and so on. For example, the planktons, green algae or microscopic plants have been responsible for the copious amounts of Oxygen on Earth's atmosphere, where previously - some few millions of years ago, there was Methane and other gases instead. Now humans are about to replace it with CO2!
So, in the study of exoplanets, the parameter of life is inherently entwined. As a matter of fact, in trying to understand the gases in an exoplanet's atmosphere, an inference to the presence of life is almost always taken into account as a possible catalyst.
Hence, there is no other way but to add "the search for Life" to Exoplanetology at this point. And this is also to inspire all the those who undertake the task of answering one of man's deepest questions, "Are We Alone?". So for now, while we're still searching, we can leave it at that. (Besides, I think its time for interdisciplinary collaborations between related sciences: Isnt it fun to bring aspects of Astrobiology, Astronomy, Cosmology and even Climatology together into Exoplanetology?)
But once we finally discover exoplanetary life, I will immediately change the definition of Exoplanetology to "The Art and Science of Exoplanets and Life on Other Worlds."
And by the way, if Gaia is to Earth, then could ExoGaia be for Exoplanets?