Cats signal with the tail, ears, whiskers, pupils and the shape of the whole body, and the honest reading usually comes from several of those at once. A swishing tail alone means little until you see the ears are back and the body is low.
A tail held straight up with a slight curve at the tip is a friendly greeting, the one a cat uses when it walks toward you. A tail wrapped around the body or tucked low suggests tension or discomfort, often with a tucked rear and a lowered head.
A slow swish while the cat is relaxed is attention, not anger. Fast, wide lashing is frustration or over stimulation, and that is the point to stop stroking and let the cat walk away.
A puffed tail, sometimes called a bottle brush, means the cat has been startled or frightened. It is a defensive response, not aggression, and the cat needs space rather than reassurance from above.
Ears forward and slightly out mean a calm, curious cat. Ears rotated sideways, the so called airplane ears, show irritation that is building and often comes just before a swat.
Ears pinned flat back against the skull are a serious warning. That cat is frightened or ready to defend itself, and reaching in is how people get bitten.
Whiskers add detail. Relaxed whiskers sit out to the sides, whiskers pushed forward mean alert interest, and whiskers pulled back tight against the face mean fear or a cat that feels unwell.
A slow blink is the closest thing a cat has to a handshake. Blink back slowly and many cats will answer, which is useful when greeting a nervous cat.
Pupils dilate for several reasons: low light, fear, pain, and the moment before a pounce. In a bright room, wide pupils on a still cat usually mean fear or discomfort rather than play.
A hard stare with narrowed eyes is a challenge between cats, and a signal for people to stop what they are doing. Look away and blink instead of holding the stare.
A confident cat stands with a level back, head up and weight evenly spread. A crouched cat with shoulders high and head tucked is trying to look smaller, which is a sign of fear or pain.
The exposed belly is the most misread signal in cats. Lying on the back with paws curled can mean trust, but a belly presented during play or after over handling is a trap: it is a defensive position with four sets of claws ready.
Watch the weight shift as well as the shape. A cat leaning away while being stroked is already asking for the interaction to end, even with its eyes closed and ears level.
A purr usually means contentment, but cats also purr when in pain or anxious, so treat purring as context dependent rather than a guarantee. A cat that purrs while hiding and refusing food needs a vet.
The chirrup or trill is a friendly greeting from a cat coming toward you, often used by mothers calling kittens. A short, sharp meow with eye contact is a request, usually for food or a door.
Hissing, spitting and a low growl are clear stop signals. A yowl that repeats, especially in an older cat at night, is often a sign of pain, deafness, high blood pressure or thyroid disease rather than a behaviour problem.
No single part of the body tells the full story. Check the tail, ears, pupils, whiskers and weight of the body together, and note the setting: a strange room, a vet clinic or a new pet changes what each signal means.
Give the cat an exit and a choice. Most bites and scratches happen when a cat is cornered or lifted against its will, and a cat that is allowed to walk away rarely needs to use its claws.
Change over days matters more than a single moment. A cat that suddenly holds its tail low, hides, stops grooming or eats less is not simply in a mood, and that pattern deserves a vet appointment rather than a behaviour theory.