Well, in answer to the question in the title I think it’s about 13 but you may disagree with me and if you do then please leave a comment! Here is my list.

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Tail curves gently down and then up again at the tip: this is a cat telling us that he/she is relaxed and at peace with the world.
Tail raised slightly and softly curved: this cat is probably becoming interested in something.
Tail held erect but with the tip tilted over: a cat with this subtle tail position is probably very interested in what is going on and is in a friendly, greeting mood but with perhaps some slight reservations.
Tail fully erect with the tip stiffly vertical: there might be a slight curve at the top but this indicates a friendly and confident demeanour and it is the classic tail-up greeting behaviour when cats get along and they are friends with each other. Desmond Morris says that “this posture is borrowed from the action of a kitten greeting its mother. The kitten’s signal is an invitation to the mother to inspect its rear end so there is an element of subordination in this display as there is in most greeting ceremonies.”
Tail lowered fully and possibly even tucked between the hind legs: this as you might expect is the signal of a defeated and/or submissive cat. The cat wishes to stress to the other cat its lowly social status. It also signifies fear and anxiety.
Tail lowered and fluffed out: the cat is indicating through body language that they are actively feeling fear.
Tail swished violently from side to side: this is a conflict signal of tail wagging. The cat’s mind is balancing between two courses of action. It’s in its most angry version. The tail swings vigourously from side to side and it means that the cat is about to attack and it is summoning up there last ounce of aggression.
Tail held still, but with tip twitching: this indicates mild irritation and is a version of tail wagging. If the tip twitching becomes increasingly powerful it can act as a clue that a swipe with a forepaw might be imminent.
Tail held erect with its whole length quivered: this is a quivering tail and it is a body language which I remember very clearly when I lived in London. A cat had been abandoned by her owner. I noticed this cat. One day she came to me outside my home and while under a parked car she presented me with this erect, quivering tail and I knew instinctively that she was delighted to see me and in fact was asking me to rescue her. I did. It is, interestingly, the same action that we see when a cat sprays urine to mark territory. But in this instance there is no urine. The gesture is saying that “I am here, it’s me!”
Tail held to one side: this is, as you properly know, a sexual invitation by a female cat in heat to the male cat to copulate. She does this when she is ready to be mounted. She moves her tail conspicuously to one side and the male cat understands that this is the moment to mate without being attacked.
Tail held straight and fully bristled: this is the signal of an aggressive cat.
Tail arched and bristled: the signal of a defensive cat but a cat that might attack if provoked. The bristling of the fur makes the cat look bigger and it is described as a ‘transformation display’ with the intention of deterring the hostile opponent. It is part of a bundle of defensive measures such as the cat standing sideways to look larger and the hairs on the spine bristled.
Tail wrapped around another: we see this when two cats are “in love” with each other to use a human expression. These cats are touching each other because cats like to touch those that they are very friendly with. It’s an expression of affection from one to the other.
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