When a cat lives with a human, cats very quickly learn to read the humans' mood at any given moment from their body language, the sound of their voice and eye contact with them. Cats are extremely good at picking up on emotions such as nervousness, fear, affection and joy. 

A cat uses these forms of communication too, so if we make a point of observing its behaviour, mutual understanding is entirely possible. To interpret a cat’s body language properly, it is important to notice changes in posture, including some that are very subtle. 

This body language is mostly quite inconspicuous. Unambiguous physical signals can only be found in fully developed emotional states. This makes it all the more important to learn to observe and to recognise increasingly subtle signs.

The tail is a cat’s most important balancing rod in situations of emotional conflict, although it is not all that easy to get a clear picture of a cat's emotional state from the tail’s position and motion: 

• Tail upright: this is mainly a sign of pleased greeting – kittens greet their mother this way. However, even in this position, the tail can express extreme rage and readiness to fight.
• Tail moving rapidly to and fro: indicates excitement– either positive or negative. When the tail moves this way, it can also be hinting at conflicted feelings.
• Tip of tail twitching, rest of tail relaxed: indicates excitement, albeit relatively slight.
• Whipping: if a cat is feeling aggressive, their tail will whip from side to side.
• Tail puffed up: indicates a high level of fear. Usually accompanied by the cat drawing their tail in between their hind legs.

The degree to which the eyes are open is another factor that can tell us much about a cat’s emotional state. 

A cat’s eyes will be fully open:

• if the cat is alert because they do not fully trust their surroundings or those present – in other words, if they are agitated
• if the cat is excited
• if the cat is curious
• if the cat is ready to hunt
• if the cat aims to threaten (threatening stare)

A cat’s eyes will be partly or fully closed:

• if the cat is relaxed (deep sleep, brief dose); the other senses keep watch and the cat can still – if necessary – awaken to full alertness in a flash
• as a means of pacification: when two cats confront each other, the weaker of the two can be seen attempting to reduce the tension by closing their eyes; the aim is to calm the stronger opponent by avoiding to stare at them directly

When living with a cat, we should take care to avoid staring directly at them with wide open eyes, as this will make the cat feel threatened. If we repeatedly close our eyes, however, this will communicate our peaceful intentions. The cat too will blink, in order to preserve their peaceful status with us.

Signals about a cat’s mood can also be found in the shape of its pupils. However, light intensity must also be taken into account, as this is another key factor in determining pupil size: in low light, the pupils will dilate irrespective of a cat’s mood. If the cat is excited or agitated, their pupils will expand into big circles even if there is plenty of light. Conversely, in a confrontation between two rival cats, the stronger animal’s pupils can be observed as vertical slits, although since this cat too will generally have mixed feelings (including fear), the size of their pupils will fluctuate subtly throughout the encounter.

With over 30 muscles involved, the position of the ears reveals a great deal. Changes occur not only when a cat hears noises from a variety of directions but also when they want to communicate a given emotional state. 

• Relaxation: the ear apertures are turned forward and the ears themselves slightly to the side, to pick up sounds from the distance.
• Attentiveness: if noises get closer, engaging the cat’s attention, the cat will stare at the object in question, turning their ears pointedly in the same direction.
• Nervousness: the ears twitch. In some wild cats, this is reinforced by tufts of hair on the ears.
• Defence and fear: the ears are laid flat, pointing backwards. This also serves to protect them against dangerous blows from their opponent’s claws. When living with a cat, humans should be especially cautious when the cat swivels their ears backwards and starts to drop them, as this indicates that they are in fear of some threat.
• Aggression and attack: although the ears are already turned backwards to allow the cat to drop them in the event of danger, at this point they are still upright in order to convey confidence. In some wild species (e.g. tigers), the ear positioning is reinforced by markings on the back of the ears.

In neutral situations, the ears will be in a central position, to allow them to react swiftly to the slightest change in the cat’s surroundings. 

The primary function of a cat’s whiskers is to help them hunt in the dark. However, their position can also convey information about a cat’s emotional state. They will be angled forward if the cat is curious, wants to investigate something or is cautiously checking something out. Conversely, they will be angled backwards when it is in defensive mode or wishes to avoid contact with something threatening. If the cat is ready to fight, they spread out into broad fans. 

A cat often finds themselves caught between courage and caution. Their mood will generally be ambiguous, superimposing threatening and defensive attitudes. This ambivalent posture can, for example, be observed when a cat faces off against a dog (especially if defending their young). Their readiness to fight can be seen in the stiffness of their legs, while their fear is expressed in their arched back.

• Signs of fear: if a cat finds a situation frightening, they will want to take flight as quickly as possible. They will crouch down low to the ground, with their ears and puffed-up tail drawn in tightly against their body.
• Signs of confidence: when a cat lies on their back with their belly exposed, this can be taken as a sign of trust. Because they feel safe, they also feel able to adopt this vulnerable position. (This does not, however, mean they will be happy to be touched on their belly. The cat may, indeed, respond by lashing out with their paws. It is essential to respect this, so as not to diminish the cat’s trust!)

Although the cat is not considered a particularly gregarious animal, they do have an exceptionally wide-ranging repertoire of sounds. This is because domestic cats have two different vocabularies. In contrast to wild cats, who abandon the language of kittens for a different one in adulthood, domestic cats who are cared for by humans retain the language used between feline mothers and their young, even when they reach maturity. In fact, they even expand this through dealing with humans. The domestic cat also has at their disposal the means of expression of an adult cat. 

• Meowing: when cats live with humans, the sound they make most often is a mewing intended to attract attention, either to themselves or to something else. This sound has its origins in the meowing of a kitten calling for their mother.
• Cooing: also derived from the vocabulary of infancy is the cooing sound used by a mother cat to call or greet her young. A trusted human will also be greeted with this sound or encouraged to follow a cat in order to engage in play or similar activities.
• Purring: the purring of a cat is very often misunderstood. It does not always mean the cat is happy and contented: in fact, it is more likely to be meant as an expression of peaceful intentions. It is also possible that the cat is actually purring in order to calm themselves (e.g. because they are in pain), they're young or a hostile cat. Of course, purring does not exclude contentment, and if the cat is feeling good, their trusted human will notice this from the rest of their behaviour.
• Hissing: hissing and spitting is probably some kind of imitation of a snake. Research has shown that many mammals have an innate fear of being bitten by a poisonous snake and that when cornered, a cat will therefore use this method to try to fend off the attack.
• Snarling, chattering: can be seen as being partly connected with hunting. In a variety of confrontations between cats or with other animals, a wide range of other sounds can be heard. In general, the sounds made by a wild cat will be quieter, so as to avoid startling their prey or giving away the location of a safe lair to their enemies.

Cats mark their patch with various smells at regular intervals, leaving invisible messages in the world around them. They do this using their own excretions, scent glands on various parts of their bodies (cheeks, chin, lips, the base of the tail), oil glands on their hair follicles and sweat from their paws. There are also other more visible signals, such as excrement left uncovered and sprayed with a liquid from its anal glands. 

Being a nocturnal animal first and foremost, a cat relies on their highly developed sense of touch to a considerable degree. Their whiskers contain tactile receptors, and their overall span is approximately the same as that of the cat’s body, allowing the cat to gauge whether they will be able to get through a narrow space.

• Touch: furthermore, highly sensitive tactile receptors are distributed all over a cat’s body. They react to physical contact, providing the cat with information about the ground conditions. Likewise, the nose includes receptors used, for example, to identify other cats that are familiar acquaintances. Cats often use head-to-head contact to greet their acquaintances (sometimes referred to as “head bunting”), and this is why many of them will rear up on their hind legs when greeting a trusted human, to get nearer to that person’s head.
• Physical contact – stroking: kittens enjoy being carefully licked clean by their mother since they associate maternal care with protection and safety. However, even among adult cats, mutual grooming takes place not so much for purposes of hygiene as to reinforce social bonds. This is why, when living with humans, cats like it when we stroke them – even if they generally want to be the ones to decide when this should happen! To show that they are enjoying this demonstration of affection, they often lift their hindquarters and tail vertically – just like a kitten inviting its mother to groom its hindquarters.