Well...Two cats are just a pair. Three or more cats are a clowder. There are other names used for a group of cats, such as a clutter, a glaring, or a pounce.
Where did I first hear the word clowder? I read it in a novel named "Gormenghast" by Mervyn Peake - "In single file there slid into the hall, so close upon each other's tails that they might have been a continuous entity, her ladyship's white clowder."
Here at Cooinda Cat Resort, we have lots of Clowders of cats stay with us for their holidays. It is beautiful to see and they really do enjoy our extra large rooms in our Luxury Accommodations. These rooms are Purrr-fect for a Clowder of cats from the same family. Our Suites can have up to 8 cats from the same family relaxing in them for the duration of there holiday.
And of course, we can't forget to educate you on what a group of KITTENS is called can we! Groups of Kittens are called a litter, or an intrigue, or a kindle (like the electronic eReader device available these days).