Mercury is not tidally locked to the Sun in the same way that the Moon is to Earth. Instead, it is in a 3:2 spin-orbit resonance, where it rotates three times on its axis for every two orbits around the Sun. This unique property means it has a day (one rotation) that is about 58.7 Earth days long, while it completes an orbit around the Sun every 87.97 Earth days.
The concept of axial tilt, also known as obliquity, refers to the angle between an object’s rotational axis and its orbital axis. For Mercury, the axial tilt is extremely small, about 0.034 degrees, which is nearly perpendicular to its orbital plane. This small axial tilt means Mercury doesn’t experience noticeable seasons like Earth.
The orbital inclination, on the other hand, is the tilt of Mercury’s orbit relative to the plane of the solar system (the ecliptic plane). Mercury’s orbital inclination is about 7 degrees.
The axial tilt and orbital inclination are two different properties. Thus, Mercury’s axial tilt is not the same as its orbital inclination, even when considering its 3:2 spin-orbit resonance with the Sun. The axial tilt defines how much the planet is tilted on its own axis, while orbital inclination refers to the tilt of the planet’s orbit around the Sun.