Final answer:
The inclination of Earth’s axis in relation to its orbital plane around the Sun is defined as the axial tilt, which is approximately 23.5° for Earth. This axial tilt leads to the seasonal changes we experience on Earth.
Step-by-step explanation:
Richard would define the inclination of Earth’s axis in relation to its plane of orbit around the Sun as the planet’s axial tilt. The axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, or, equivalently, the angle between its equatorial plane and orbital plane. It is about 23.5° for Earth, which is the reason we experience different seasons, as the tilt causes various latitudes to receive different amounts of sunlight throughout the year.