What shape is the moon described as between the half moon and the new moon?

The shape of the moon between the half moon (first quarter) and the new moon is known as a crescent moon. This phase occurs when less than half of the moon's surface is illuminated by the sun and is visible from Earth. During this period, the moon appears as a thin sliver, curving in shape.

A crescent moon can be seen in both the waxing phase, where the illuminated part is increasing after the new moon, and the waning phase, when the illuminated section is decreasing leading back to the new moon. This illumination is influenced by the moon's position relative to the Earth and Sun, resulting in varying appearances as it orbits.

The term "full moon" refers to when the entire face of the moon is illuminated, while "gibbous moon" describes a phase where more than half of the moon is illuminated but not yet full. "Quarter moon" pertains to the first or last quarter when half of the moon is visible. Thus, a crescent moon is the definitive shape that best fits the description of the moon between the half and new moon phases.