Here's why:
* Brief piece of prose: Essays are typically shorter pieces of writing than novels or research papers.
* Single subject: Essays focus on a specific topic or idea.
* Highly opinionated: Personal essays and opinion pieces often express the writer's strong views and perspectives on the subject.
Other terms that might apply to such writing include:
* Column: This is a regularly published piece in a newspaper or magazine, often expressing the writer's opinion on current events or issues.
* Blog post: Similar to a column but typically published online.
* Editorial: A formal piece written by the editor of a publication, expressing the publication's opinion on a particular issue.
Ultimately, the specific term used depends on the context and the specific piece of writing in question.