ANARCHY

Absence of a world government.

PEACE

Although this may not refer to absolute peace in the system, it usually refers to a considerable amount of easiness or quiet activity in the system, and can be classified as a non-threatening period.

COOPERATION

When states or regions work together towards a common goal.

LEARNING

A process in which a state changes its beliefs, or develops new beliefs, skills or procedures, as a result of the interpretation of experience.

ADAPTATION

When learning is applied, and policies are changed. Without adaptation, there will be no change, and learning becomes useless.

INTERNATIONAL INSTITUTIONS

Act as a third party in order to resolve conflict between states. International institutions can involve states, can be non-governmental, etc.

FOREIGN POLICY

A state's strategic policies towards the international arena, and deals with economic, political, and societal aspects. 

REGIME 

Form of government, such as an authoritarian regime, or capitalist regime, that manages relations between the state and it's citizens.

BALANCE OF POWER

Refers to the way in which stability is achieved through the conflicting efforts of individual states (as most states want more power). If the balance of power is hindered, i.e. if one state tries to achieve more power, other states will retaliate, and the international system will be affected and unbalanced.