The reasons why cats grind their nails:

1. Cat’s nails grow very fast and are very sharp. Over time, they will dig into the flesh pads and affect the cat. For normal activities, cats will grind their nails frequently to prevent nails from growing too fast and keep their fingertips sharp.

2. When cats grind their nails, they also want to declare their sovereignty and occupy territory. Cats have sweat glands in their footpads, which can emit their own scent. Therefore, once a cat wants to occupy an object or territory, it will let the object or location be contaminated with its own scent in the process of sharpening its claws.

3. When cats grind their claws, they are also stretching their backs, which can relax their muscles and activate blood circulation. Cats grab an object and then stretch their back and hind legs. This can protect the health of their joints, stretch their muscles, and make themselves more comfortable.

4. Cats grinding their claws is also a way to release stress. When a cat has been wronged or is irritable, it will also vent its emotions in this way.

5. Cats will also sharpen their claws when they feel happy. For example, when the owner just comes home, he will see the cat sharpening its claws. This is a sign that the cat is happy.