Canine communication is the transfer of information between dogs or between dogs and humans or other animals. Dogs communicate affiliation, happiness, excitement and pleasure through vocalizations, just as people do. But they also use body posture and scent cues as significant components of their vocabulary.
Dogs also differ from humans in their methods of communication in other ways. People listen Dogs watch. Another difference is that humans can communicate specific information and dogs communicate in a more general way.
For instance, body posturing indicates emotional states, but not specific intent. 
People may be a long way from learning to speak the dogs’ language, but they can learn to communicate effectively.
Canine communication is more of a sign language than it is a verbal one. It does, however, incorporate vocalizations and scent ability. Dogs use their communication system to communicate with other dogs and as a way of resolving conflicts within their group.
This is one reason it’s important to socialize a young puppy. He has to learn how to communicate with his peers.
Compared to dogs, people are scent blind and deaf as well. That makes some of the subtle aspects of canine communication impossible for us to understand. But, if we listen and watch carefully, we can learn to understand a lot of what our dog is saying.
Dogs like to combine their three modes of communication. They use these basically to increase the distance between the and their “communication partner,” or to decrease the distance,
For instance, if a puppy wants to decrease the distance, he will display a wagging tail. 
Growls are intended to increase the distance.
A lot of studies have been done in dog-human and dog-dog communication. And, it has been found that there are a lot of similarities that may have been learned over the many years of canine-human interaction.
Take pointing for example. 
It’s a building block of human communication. Infants point before they speak their first word. In 2009, researchers compared the response to a range of pointing gestures by human infants and dogs. The results showed little difference between a 2-year-old child and a dog. By the time the child had reached the age of 3, their performance was higher than the dogs.
Another study indicated a dog can communicate its size via its growl. The study showed that dogs cannot and do not misrepresent their size. The test showed images of different size dogs and played recordings of their growls. Twenty of the 24 test dogs looked at the image of the appropriate size dog and looked at it longest.
Body positioning is an extremely important aspect of the dog’s communication system. As far back as 1872, Charles Darwin , in his book, “The Expression of the Emotions in Man and Animals,” published examples of body positioning to communicate emotions in dogs.
Small dog watching a cat on a table Dog approaching another
dog with hostile intentions
Dog in a humble and affectionate
frame of mind
In her book, “On Talking Terms With Dogs,” Turid Rugaas identified signals she claimed dogs used to calm themselves or to calm other people or animals around them.
She claimed that a dog that was sitting with its mouth relaxed and slightly open, its tongue slightly visible and maybe draped over the lower teeth was showing he is relaxed and content. On the other hand, a dog with its lips curled to show the teeth is sending a warning signal. It is showing its weapons – the teeth.
She says if a dog sits with its mouth closed, it usually is showing interest in something or is appraising a situation.
A dog’s head position also is an important form of communication. A dominant or threatening dog looks directly at another individual and a dominant dog that is attempting to calm a more submissive dog will turn its head to one side away from the submissive dog.
Other researchers have identified five groups of canine communication signals. The first is fear and a dog communicating fear might lick his lips, hold his mouth tightly shut, yawn, cover, tremble or shake. It’s also easy for a fearful dog to switch to aggressive behavior quite fast, so it’s important to pay attention to any changes in what or how a dog is communicating.
Another group of communication signals is excitement or arousal. It often is a reaction to a stimulus a dog likes. Some frequently observed behaviors in the excited or aroused dog are jumping, mouthing or mounting. Often dogs will play bow. Reactions to an unfavorable stimulus could be holding the tail low, cowering, barking or lunging.
A dog communicates that he is anxious or feeling stressed by excessive panting or pacing. And like the dog who is excited by an unfavorable stimulus, he may bark or lunge.
The fourth of the communication groups is aggressive communication and can include stiffening the body, growling, showing the teeth, curled lips and snapping at the air.
The last of the five groups is relaxed communication. The dog acts like he doesn’t have a care in the world. His eyes are soft, his body limp and sometimes he almost looks as if he is smiling.
We’ve talked a lot here about non-verbal communication, but dog’s verbalize when they communicate, too. The American Kennel Club says low-pitched moans are a sign of contentment in puppies. A sigh is another way a dog communicates contentment or pleasure. On the other hand, a sign accompanied by wide open eyes can mean the dog is disappointed.
Whines usually indicate distress, but also can be used to communicate happiness and excitement. The difference is in the pitch, with the higher pitched whine indicating distress.
The same is true for growls, which can be used to communicate warnings or threats, but also the desire to play. Again, the pitch gives the true intention with a noisy, medium-pitched growl indicating the dog wants to play.
And then there’s the howl. Perhaps it’s a throwback to their ancestors – the wolves. Many say when a dog howls alone, it is indicating it wants it’s pack. Then, often, other dogs will join in. I know that’s often the case at Rochester’s house. We will have 9 wire fox terriers howling in unison. What a lovely sound.