What term describes writing that explains how or why something happens?

The term that describes writing which focuses on explaining how or why something happens is "explanatory." This type of writing aims to clarify a process or provide insight into the reasons behind events or phenomena. In an explanatory piece, the author typically presents information in a straightforward manner to aid the reader's understanding. This may involve outlining causes and effects, providing context, and breaking down complex ideas into simpler, more digestible parts.

In contrast, the other terms have different primary functions. "Argumentative" writing is designed to persuade the reader of a particular viewpoint or claim, often involving the presentation of evidence to support an argument. "Coherence" refers to the logical flow and clarity of writing, ensuring that ideas are connected and understandable but does not refer specifically to the purpose of explaining. "Citation" pertains to the practice of crediting sources, which is essential in academic writing but does not denote a style or type of writing aimed at explanation.