It is assumed to be tidally locked to its parent star.

The two planets are tidally locked, so they always present the same face to each other.

This celestial body is tidally locked and has phases, very similar to Earth's moon.

A third possibility is where the primary and moon are tidally locked to each other.

Pluto-Charon was the only significant system in which both partners were tidally locked.

The planet is not tidally locked to the star.

The planet is tidally locked to its star, always presenting the same face to it.

The novel is set in a world that is tidally locked.

Earth's Moon is also tidally locked, as are many satellites of the gas giants.

The pair were tidally locked, always showing the same face to each other.