cat's body language (from:
Common Cat Behaviors)
When a cat's ears are up (pricked), forward and slightly outward this means the cat is content, relaxed and carefully listening to what is going on around them. Here the slanted eyes and regularly sized pupils also indicate contentment.
When something catches a cat's attention the ears become more erect and the cat is alert and ready to investigate the source of the noise. The eyes become slightly wider indicating alertness.
If a cat becomes anxious or fearful, the ears will point to the sides and flatten. The more anxious the cat is the flatter her ears will become. The pupils are now dilated indicating fear.
When a cat becomes annoyed and feels defensive he will turn his ears back. This should be a warning to you to get back. The eyes confirm this warning with the dilation of the pupils.
When a cat becomes both fearful and aggressive and is ready to fight he will flatten his ears straight back. It is believed cats pin their ears back in order to protect them during a fight. The eyes are now greatly dilated since the more fearful the cat the greater the pupils dilate.
When a cat carries his tail high and straight up in the air it means he is proud and content.
A mother cat's upright tail is a signal for her kittens to follow her.
When a cat is relaxed, confident and alert, it walks with its tail horizontally behind it or even slightly drooping. You may also see this tail position when your cat is on the prowl or stalking.
When a cat is very excited and happy to greet its owner he will hold his tail straight in the air and it will quiver or twitch. This is the cat's way of saying he is so pleased to see you that he is overcome with emotion.
If a cat is friendly but cautious of the other cat or person, the upright tail is hooked over at the tip indicating a degree of uncertainty.
When a cat is fearful and feels seriously threatened he will exhibit what looks like an upright bottle brush (or puffy) tail. This indicates that the cat has become defensively aggressive; meaning it would rather get away, but if provoked it will defend itself
When a cat swishes its tail from side to side this may indicate real or mock annoyance. It may also be a playful warning saying "I'm going to get you, so look out!" The more emotionally charged the cat is the faster the tail will swish.