plural noun

Aerobics is a form of physical exercise that combines rhythmic aerobic exercise with stretching and strength training routines with the goal of improving all elements of fitness (flexibility, muscular strength, and cardio-vascular fitness).

Example

1. I like to start my day with an aerobics class at the gym.
2. I find that aerobics helps me to maintain a healthy lifestyle.
3. Aerobics is a great way to get the heart rate up and burn calories.