The PPP is a principal that states that one causing pollution or environmental degradation will pay a cost to remedying it. The practical implications of this principal lie in its allocation of economic obligations on environmentally damaging activities.
The word principle is a noun. The plural form is principles.
past
The salt water oceans and seas are a principle part of the hydrosphere
emphasis
Explain is a verb.
Up till recently the US was the world's largest polluter of the atmosphere, burning fossil fuels and adding carbon dioxide to the greenhouse gas levels.
is a basic part of a rule or behavior.
Verb
explain risks as part of an integral part of every day life
principle of complementarity of structure and function
The mesophere is part part of the atmosphere it is the cold part of the atmosphere.
The epidermis of the skin has no blood supply.