难题

To make something clear or easy to understand by describing it in more detail or revealing relevant facts.

To estimate the nature, quality, or ability of someone or something; to assess or evaluate.

A person or thing that gives rise to an action, phenomenon, or condition; the logic or motive behind a fact.

Because of; owing to; as a result of. Used to introduce a reason or cause in a more formal way than '因为'.

The reason for which something is done or created or for which something exists; an intention or objective.

An abstract idea or a general notion that represents something. It is often used to discuss theories or new ideas in academic writing.

A quality or feature that typically belongs to a person, place, or thing and serves to identify them. It is frequently used in descriptive academic writing.

A point or way in which things or people are not the same. It is a key term for comparing data sets or social groups.

A place, person, or thing from which something comes or can be obtained. Used when citing information or discussing origins.

The extent of the area or subject matter that something deals with or to which it is relevant.