P is for purring. Purring, that rumbling sound made by happy cats. Sometimes the purr is not loud enough to be heard, only felt. Sometimes it is loud enough to be heard across the room.
Cats purr when we are happy, but also when we are hungry. Our human has known several cats who purr louder when it's time to eat. Truffles purred when the human came out to feed us and picked him up. Binx purred when the human came in to feed him. When we are really trying to manipulate our humans emotionally (feed us now please!), we sometimes purr and meow at the same time, so we confuse them and they have no choice but to take care of us.
Queens also purr when their kittens are born, and also when the kittens are nursing. The blind kittens can recognize the purr as a sound associated with something good, and can find their way even if they can't see.
The purrrrr has healing powers. It is in a low frequency, at or below the lowest key on a piano, that can help cats (and their humans) heal, not just a bad mood, but also some physical injuries. Sometimes cats in pain purr; sometimes dying cats have been known to purr as well.
We can purr when we are inhaling or exhaling, but the voice is not as loud in both directions. Large cats (lions, tigers, jaguars, leopards) who roar cannot purr.