What it usually means
Dogs have lived alongside people longer than any other animal, and in dreams they tend to stand in the space between the two: close, loyal, readable, and still an animal. That makes them one of the most flexible dream images, and one of the most personal.
The first thing to separate is your own history. If you have a dog, had one, or were bitten as a child, the dream dog arrives already loaded with that. A dream about your own dog may simply be about your dog — dreams about beloved pets, living or dead, are very common and need no decoding.
Beyond that, dog dreams tend to be about loyalty and trust in both directions: whom you can rely on, who relies on you, and what happens when that bond comes under strain. The dog's behaviour toward you is often the most honest part of the dream: it does not pretend.
What changes the meaning
A friendly dog. Companionship and ease. Often appears when support is present, or when you are being a good ally to someone else.
A dog that bites. A breach of trust, or the fear of one. Something expected to be safe has turned.
A barking dog. A warning. Something is trying to get your attention — possibly your own sense that a boundary is being crossed.
A dog guarding a door or gate. Protection at a threshold. What it guards, and whether it lets you past, is the centre of the dream.
A lost or abandoned dog. Loyalty left without care. Someone, or some part of you, that has been neglected.
A sick or injured dog. A relationship or a source of support that is weakening.
A dog that died, alive again. Very common after losing a pet, and often comforting. These dreams are grief doing its ordinary work.
A pack of dogs. Instinct in numbers — group pressure, a crowd mood, or a situation where too many demands are barking at once.
Being followed by a dog. Loyalty you did not ask for, or an instinct that keeps pace with you whether you acknowledge it or not.
When it keeps coming back
A recurring dog, especially one that looks the same each time, is usually carrying a stable meaning for you personally, and the best guide to it is your own history with dogs rather than any general reading.
If the dog keeps returning hostile, it is worth asking which relationship currently feels loyal on the surface and unsafe underneath. If it returns friendly and you keep ignoring it in the dream, the question turns around: what support are you not letting in.
Dreams of a dog you have lost deserve a separate word. They often return around anniversaries, or when a new animal comes into the house, and many people find the old pet in them calm, healthy and at ease. That is not a message from anywhere. It is memory settling into its final shape, and it is one of the gentler things dreams do.
In Jungian terms
In myth the dog guards and guides at the edge of the known world: Cerberus at the gate of the underworld, Anubis leading the dead, the hounds that run with the hunter goddess. Jungian readers take that role seriously. The dream dog is often a guide into unfamiliar inner territory — an instinct that knows the way better than the conscious mind does.
Its temperament matters. A companion dog suggests instinct that is on your side and has been looked after; a wild or vicious one suggests something instinctual left too long without attention until it turned. Neither is a verdict. Both are an invitation to look at the relationship.
The plain form of the question is this. Whom do you trust without thinking, and is that trust still earned.