What does it mean when a cat moves its tail left and right?

The main meanings of a cat's tail moving left and right are as follows:

Excitement: When a cat arrives in a new environment or encounters something it fears, its tail will quickly move left and right.
Anxiety: A cat's tail will gently move left and right to express its anxiety when it is hungry or wants to sleep.
Illness: When a cat is sick, its tail will usually move left and right downward. If you notice that your cat's tail is moving left and right downward, it's advised to take it to the vet as soon as possible for a check-up and treat it accordingly based on the examination results to avoid delaying the illness.
Emotional Excitement

When a cat is emotionally excited, its tail will violently move back and forth. For example, when it arrives in a new environment or encounters something it fears. At this time, the owner should promptly remove the cat from the stimulating environment or item and introduce it to things it usually enjoys playing with, such as a catnip toy, to help the cat gradually relax its mental state. Otherwise, the cat might become overly excited and hurt people by jumping around.

Anxiety

If a cat suddenly becomes restless and its tail moves gently left and right, the owner should consider whether it's due to hunger or excessive playtime, causing the cat to lack sufficient sleep. As a cat's tail moves gently left and right when it's hungry or wants to sleep to express its anxiety, the owner should judge accordingly based on the cat's behavior.

Illness

If a cat's tail moves left and right downward, it's a cause for concern as it may indicate illness. The owner should first rule out any possible punishment the cat received, as this can also cause such a reaction. If not, it's possible that the cat is conveying its illness to the owner, possibly accompanied by symptoms such as lethargy and loss of appetite. At this point, it's essential to take the cat to the vet for a check-up and treatment as soon as possible to avoid delaying the illness.