A plural noun is a word that indicates that there is more than one person, animal place, thing, or idea. When you talk about more than one of anything, you're using plural nouns. When you write about more than one of anything, you usually use the same word, simply adding an s, es, or ies to the end.
Fossil fuels are the leading non-renewable energy sources around the world. There are others, however. Nuclear energy is usually considered another non-renewable energy source. Although nuclear energy itself is a renewable energy source, the material used in nuclear power plants is not.
Discipline is action or inaction that is regulated to be in accordance with a particular system of governance. Discipline is commonly applied to regulating human and animal behavior to its society or environment it belongs, while self discipline is the ability to control one's feelings and overcome one's weaknesses; the ability to pursue what one thinks is right despite temptations to abandon it.
Discipline is a moral obligation among many groups of people. Disciplined behavior is required by some laws and other legal obligations.
Commercial entities can also put in place strict disciplinary requirements for the length of the commercial agreement.
Airlines enforce strict disciplinary and conduct rules upon flight passengers, Etcetera.
