Communication - the imparting or exchanging of information or news.
Communication is skew to a healthy relationship. It lets the couple know what each other is thinking. Their wants and their needs, or what they would like o happen or change. Without communication a relationship is more likely to fail.
Compromise - an agreement or a settlement of a dispute that is reached by each side making concessions.
In a relationship you and the person your in a relationship with will be two completely different people. You will both have different opinions on different topics. At one point or time you will have to make a compromise. Compromise benefit both parties and are a good way to avoid major problems.
Cooperation- assistance, especially by ready compliance with requests.
In a relationship you will have a completely different plan and life from the person you are involved with. In order for you two, to stay together you must cooperate to reach one goal which is to have a happy relationship together. If you get married there will be problems like bills, kids, cars, houses. These are problems that you can solve on your own but will much easier if you cooperate with your spouse to get the job done.