The term 'Doctrines, Informally' can be solved by the four-letter word 'ISMS'. An 'ISM' is a suffix that is used to denote a belief or doctrine. It is often used to refer to a system of beliefs, principles, or ideologies. For example, Marxism is a type of ISM that refers to the political and economic theories of Karl Marx. Similarly, capitalism is another ISM that refers to an economic system based on private ownership of the means of production.