Rain is a liquid state of matter. When water evaporates from oceans, rivers, and lakes, it turns into water vapor, which is a gas. This water vapor then cools and condenses in the atmosphere to form clouds. Once the droplets in the clouds become heavy enough, they fall to the ground as rain.
To understand this better, consider the water cycle: it starts with evaporation, then condensation, and finally precipitation, which is rain or other forms of moisture like snow. During the precipitation phase, the water returns to the earth in its liquid state, which we commonly observe as rain. Thus, we can confidently say that rain is water in its liquid form.