This is the 8075th most frequent Dutch word.
fitness
Exercise or physical training to improve health and strength.
Here, 'fitness' is used as a noun referring to the gym, a place for physical exercise.
Ik ga elke maandag naar de fitness om te trainen.
I go to the gym every Monday to train.
In this sentence, 'fitness' is used as a noun to refer to the general concept of physical well-being and exercise.
Fitness is goed voor de gezondheid en verbetert je uithoudingsvermogen.
Fitness is good for health and improves your stamina.
Here, 'fitnessruimte' incorporates the word 'fitness' to indicate a dedicated space for gym equipment and activities.