Cats communicate a variety of messages using body language. Examples include arching their backs as a signal of fear or aggression, and slowly blinking to signal relaxation. A cat that chooses to lie with its stomach and chest exposed conveys happiness, trust, and comfort (this is also typical of overweight cats, as it is more comfortable for them); however, a cat may also roll on its side or back to be able to defend itself with all four sets of claws. Usually other signs (like ears and whiskers folded backwards) give an indication of the cat's overall humor. Flattened ears mean that the cat feels threatened, and may attack. Mouth open and no teeth exposed suggests a feeling of playfulness.[1]

As is the case with dogs, the tail is often used as a signaling mechanism. A tail held high suggests confidence or happiness, or can be used as a greeting towards human beings or other cats (usually close relatives), while a half-raised tail shows less pleasure, and unhappiness is indicated with a tail held low. In addition, a cat's tail may "wag" or move rapidly to express a state of conflict. A cat with tail held high and twitching shows excitement, but this is often mistaken for anger. Cats will twitch the tips of their tails when hunting or when irritated, while larger twitching indicates displeasure. They may also twitch their tails when playing.[2] A scared or surprised cat may puff up its tail, and the hair along its back may stand straight up and the cat will turn its body sideways to a threat, in order to increase its apparent size. Tailless cats, such as the Manx, which possess only a small stub of a tail, move the stub around as though they possess a full tail.

Touching noses is a friendly greeting for cats, while a lowered head is a sign of submission. Some cats will rub their faces along their guardian's cheek, hands, or ankles as a friendly greeting or sign of affection. This action is also sometimes a way of "marking their territory", leaving a scent from the scent glands located in the cat's cheeks. More commonly, cats do something called a "head bonk", or "bunting", where they literally bump someone with the front part of their heads to express affection.[3]

Cats also lick each other and people (e.g. their owners). Cats lick each other to groom one other and to bond (this grooming is usually done between cats that know each other very well). They will also sometimes lick people for similar reasons. These reasons include wanting to "groom" people and to show them care and affection.

When cats are happy, they are known to paw their human companions, or a soft object on which they may be sitting, with a kneading motion also called "padding", "pitter-pattering", "pacing", "kneading dough", "happy feet", "treading", "needle paws" and "marching in place". While kneading, cats sweat through their paws leaving a scent for other cats, humans are unable to smell this however. Cats often use this action alongside purring to show contentment and affection for their companions. This can also indicate curiosity. A cat may also do this when in pain or dying, as a method of comforting itself. It is instinctive to cats, and they use it when they are young to stimulate the mother cat's breast to release milk during nursing. As a result, cats hand-raised by human beings may not exhibit this behavior. Pawing is also a way for cats to mark their territory. The scent glands on the underside of their paws release small amounts of scent onto the person or object being pawed, marking it as "theirs" the same way they would urinate to mark their territory. Since the nature of the activity is an instinctive response related to the mother's care for the kitten, it may be an expression of need, indicating an empty water bowl, hunger, an unappealing litter box, or the need for some attention from the caregiver.

Reading your cat's body language
Body position Your cat's mood
Outstretched, relaxed, lying on his side, tail down A contented cat
Upright, relaxed stance, ears up, moderate / brisk walking pace Relaxed, confident cat
Controlled, vigilant pose, slowly walking forward in a slightly crouched manner Hunting / approaching a potential threat
Tense muscles, low crouch, ears back, tail tucked up and under Anxious cat
Arched back, fur raised (piloerection), bottle brush tail, all fluffed out and curled into a downward U / tucked away to avoid injury Fearful cat that is likely to attack defensively if challenged, cornered / picked up
Tense, rolled onto his back to expose his belly (very different from the relaxed and happy cat that's rolling around in the sunshine / a nice warm bed) Aroused cat that is preparing to attack with all five of his defensive weapons - four sets of claws and his teeth; don't be fool into thinking he's being defensive
Tall, tense, raised rump, tail extended, forward-pointing ears, stiff forwardly extended whiskers, constricted pupils Confident, intimidating cat - BE CAREFUL!