They do not understand a word you say even if you say it loudly. They will learn over time and much patience the action that corresponds to the word you assign to it. How much time depends on age of the animal and how clear you are in how you it is presented as well as PRAISE< PRAISE< PRAISE.

First understand that dogs chase prey. To a dog prey can be a squirrel, bird ball or even a CAT. At first all the dog sees is a fast moving toy/prey. Dogs luckily have a fantastic sense of smell. They can distinguish and find when taught many objects and animals. The key is slowing them down long enough to smell that the fast moving toy/cat is a cat not a toy or food source. Teaching the dog to ignore(leave it) will give the dog the time to engage his nose along with comingling scents to help him learn the cat is part of the family. Dogs do not want to hurt family members.

Now Cats. They are cats. They will run, taunt and act like prey. Even when the dog is leaving the cat alone, the cat will still bother the dog. There is always an instigator; usually, it is the cat. Unfortunately the dog is to blame when the cat is either upset or harmed. The dog needs patient training to be able to control his natural instincts and time to understand cat scent=family member. This process can be quicker with puppies, but they need to learn the same boundaries so as they grow their instinct to chase does not extend to cats.
I never encourage dogs to chase any breathing thing, with the exception of dogs used for hunting specific game. Letting dogs chase rabbits may look cute, but hearing that rabbit SCREAM When Caught, will change your mind very fast. It is much harder for a dog to unlearn bad behavior than it is to learn good behavior from the beginning. If your breed needs to chase; use toys, balls and flirt poles to drain the prey energy constructively. A high-energy dog needs to use up its energy somehow. Long walks, fetch, even treadmills will help. A tired dog is less likely to shred the house and chase the cat (after other prep work).
Keep in mind your breed of dog. Read about the breed; preferably before you plan on adding it to your household. Many working dog breeds need constant physical and mental gymnastics all day long. Exercise is not enough with these breeds. Give them things to do. Sit, Down and stay to them can be an activity. Adding these exercises when the mailman comes can teach patience and obedience as well as making them feel useful. Most people lock the dog up when they answer the door; which both frustrates the dog and makes him fearful when the bell rings— “It must be danger”, “I am being locked up”.
In the beginning, them on a Collar and leash to help but with patience and practice the once barking dog will quietly sit or lay down where you want near the door so you can have a conversation or invite a guest in. As the dog gets more confident that door bells are not a rise to action if he’s calm ask the visitor “do you like dogs”; and if yes, encourage the dog saying “say hello” or any other words you want the dog to understand as permission to say hi to the person. Remember whatever wording you use—be consistent. Also remember most people do not know how to greet dogs. Patting a dog on its head is covering the dog’s eyes, and can scare the dog. Always ask your guests to present their hand palm up under the dogs chin so he can smell the human being introduced first. When possible, if the dog and visitor are calm and relaxed, practice patting and other poor dog greeting affection. This sounds crazy but will pay off later. It’s easier to teach the dog than the humans.
Practice and patience’s- Cats may act like prey but humans are worse. Teaching your dog not to chase or react to a fearful human is very important. I use the same command “leave it” for cats and fearful humans. This will not affect the dog’s ability to protect you, only your ability to control the dog. If the dog is not fearful, he will be confident and happy in his surroundings. His comfort is not only food and shelter but also the time you take to assure and teach him. A bored, untrained dog will ruin your home and sanity. The earlier you start (puppy preferably), the easier. An older dog can learn but will need more time and patience. The key is PATIENCE and exposure to the world. The more they are introduced to the better. Providing good, consistent training will make introducing your dog to the world fun and exciting. The command “Leave It”/”ignore” when you walk by something that could be intimidating will reassure the dog that since you said to ignore it, it must be OK.
I started this as a Cat and Dog guide; however, the unpredictability of the cat is very similar to the unpredictability of people and life. The dog’s ability to filter out strange noises, people and places can start simply with learning to coexist with a cat. Cat’s make the strangest noises, taunts and pops out from obscure places.

CATS AND DOGS: BE PATIENT!!! BE REALISTIC!!! Cat and dog harmony can take time(MONTHS). ALWAYS give the cat an escape; gates with cat doors and shelves are useful, Plenty of vertical space.

Scent is basic animal introduction. Wrap 2 blankets around you. Put one where the cat sleeps and the other where the dog knaps. Every day swap the position of the blankets. Familiar scent, you, mixed with their scent will ready them for the next part.

There are some breeds of dogs however that should not live with cats. These are not bad dogs but dogs that have extreme kill drive that will prevent them from being able to control their natural instincts. This is different from prey drive which dogs have naturally, kill drive are for the breeds that are designed to kill and or battle its prey. Yes there are exceptions in all breeds but is it worth the risk if you can? It is unfair to both the cat and the dog to be set up to fail in these circumstances, usually THE CAT IS KILLED BY THE DOG. If you are aware of these traits in the breed of your dog the cat was not killed by accident, YOU KILLED THE CAT!!!

CATS: Cats will act like prey
Cats will run from dogs
A Cat’s favorite game is taunt the dog

DOGS: Want to chase prey
Can learn to “Leave It” (applies to anything you want dog to ignore)
Will learn a cat is not prey and will want to be near it

If the blankets have had enough time to work the cat smells like you and the dog.
Being near the cat makes the dog happy since being near you makes the dog happy.

If the dog doesn’t chase the cat stops running. The cat WILL try harder and come closer to make the dog chase(why? It’s a cat). When the cat learns that the dog won’t chase the cat will stay closer to the dog. The dog gets to be near the cat, THIS IS THE REWARD FOR THE DOG, the cat gets treats for staying near the dog. Lure the cat at this point with treats to stay close to dog. Cat treats are not good for dogs and can make them sick. Always be careful incase the cat spooks, Why? IT’S A CAT, you never want the cat to feel trapped since the cat might try to use you as a tree to escape(yes this is very painful).
Use common sense, don’t let the dog loose until he has learned “LEAVE IT”, “COME” and “DOWN” with confidence. The dog can run around the house with a leash until he’s ready. A PROPERLY introduced Ecollar can AID this process. Ecollar’s are not for punishment but an extension of you. Saying “LEAVE IT” with a buzz(tone or light stim) can reinforce the hard work you have done and ease your mind that the cat wont be harmed. Remember the collar is not to be used to punish, you don’t want the dog to think of the cat as pain. Also if not properly introduced the dog with have no idea what the collar is for. A good trainer can help in the proper use and introduction of the Ecollar.

Defining breeds for cat suitability:
Bred to find, hold and KILL prey= PREDATOR, NOT SUITIBLE
Bred to find and show(point/flush) prey= sporting/hunting, SUITIBLE with training
Bred to herd prey/animals= SUITIBLE with training
Bred to eliminate vermin= NEVER SUITIBLE(Most Terriers)

Everyone talks about exceptions, these are nice until the cat is torn apart, and I mean “ACTUALLY TORN APART”. I can never forgive the person who told me that her Jack Russell terrier killed her cat, She got another cat, It then killed that cat too!!!! The person knew better, the dog killed vermin, the dog considered cats vermin, the person KILLED THE CAT.

The importance of knowing your breed is never more important when trying for harmony and peace in the home. Also if a breed will kill a cat it can kill a baby or small child. These predatory breeds have trouble distinguishing play and kill instincts and can switch from play to kill in a second. This is not enough time for the human to save the cat or child from being mauled by the dog who does not and will not know he is doing anything wrong. If it is bred to kill/be a predator, anything weaker is fair game.