I'm writing a technical book (for programmers) on functional programming in TypeScript In my book I go over a relatively big list of all sorts of data types, where each chapter is dedicated to its own data type. Every chapter follows the same principle: a description of a data type, and then a subsection for every type class to which this data type belongs (with explanations, usage examples, etc.)

so for example a chapter on IO will have the following subchapters:

  • IO as Functor
  • IO as Applicative
  • IO as Monad etc

My question is: given that these kinds of sub-titles in chapters are going to be repetitive throughout the book, do I need to use an article?

  • "IO as a Functor"
  • "IO as an Applicative"
  • "IO as a Monad"

1 Answer 1


In chapter titles, I would use the variant without article.

In English, you use nouns without article when you are talking about all items of that class or when you talk about that type of thing in general, which is what I assume you do in a chapter that explains what it means when IO is a functor.

"A functor" referts to a specific, unknown functor, "the functor" refers to a specific, known functor, "functor" to all functors or functors in general.

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