Some common indicators that a cat is happy and relaxed include:
- Greeting you (other people, other cats, etc) with an erect, upright tail (often with a twist at the top).
- Napping with its feet completely underneath it (especially in an open, unprotected area)
- Returning your look with a slow blink
- Fur laid flat/relaxed to the skin (not upright, especially on the back ridge)
- Whiskers relaxed (pulled forward indicates interest and can happen when the cat is happy, but pulled back is a protection instinct and indicates fear/discomfort)
- Ears upright, relaxed (swiveling to listen to sounds indicates interest, laid flat is fear/anger/anxiety).
If you know your cat well, you can generally get an idea of the indicators that "depend". For example, Hunter (our only non-Siamese) meows only in distress while the three other cats talk all of the time about everything (my food bowl is empty, my food bowl is full, my food bowl is downstairs and I'm upstairs, hey I can meow!). Distress purring has a different sound than happy purring (it's subtle, but pay close attention next time you take your cat to the vet and you may be able to hear it).
In addition, if your cat is meowing but you aren't sure what it means, you can look for other clues to help you figure it out. If your cat is meowing while standing next to the food bowl and you haven't fed them in several hours, it's probably distress (help help I'm going to starve!). If your cat is purring while snuggling with you on the couch (fur/whiskers/tail relaxed) then your cat is probably happy.