Exoplanets are planets. Also, for clarification, biology is not defined as “the study of things produced exclusively by natural evolution.” Synthetic biology works with biological components and living systems (DNA, proteins, regulatory networks, cells and organisms). It differs from much traditional biology mainly in its constructive, engineering-oriented approach. Synthetic systems are often built precisely to test hypotheses about how natural biological systems function. Claiming it is not biology is wrong IMO.
For anyone else that might be curios, the definition of a planet you will often see quoted online applies to bodies in our Solar System. It comes from the International Astronomical Union in 2006. This is the famous definition that dropped Pluto as a planet. While the criteria are widely quoted, that actual resolution isn't. The resolution:
The IAU...resolves that planets and other bodies, except satellites, in the Solar System be defined into three distinct categories in the following way:
(1) A planet [1] is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape [2], (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
(3) All other objects [3], except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".
The definition here only applies to bodies in the Solar System.
Still a bad definition IMO. According to the definition if a catastrophic event were to occur that cluttered the neighborhood of a planet it would cease to be a planet until it was cleaned up. The definition of a planet should be based in the physical attributes of the celestial body itself, not in its role or relationship with other bodies. I'm a bit of an extremist on this front. Even our Moon would be a planet in my opinion. Seems silly when you think about our barren moon but there are for sure habitable moons out there. I can't imagine asking an alien "What planet are you from?" and them responding "erm, actually we are from a moon/planetary satellite".
And notice how we have those two different words - mother and woman? You can have words that describe relationships, in fact that is really good! You can even compound words or create whole new ones to encompass multiple types of attributes! What we should avoid is taking widely used words and changing the definition to add a criterion that is of a whole other type of attribute.
Your mother and woman example is perfect! It would not be appropriate to most people to change the definition of woman to a female that had or has an offspring. You are taking a definition that describes an attribute of the subject (gender) and throwing in criteria that is based on a relationship. That makes no sense!
If it is important for you to make a distinction on whether an astronomical body has cleared its neighborhood then you can create a new word or compound word.
