"I recommend trying it if you like writing with pen and paper". This is a sentence in a book. Why isn't there an "a" article before "pen" since pen is a countable noun? Is it just a style preference?
This is an anwer that I posted on this similar question here:
This phenomenon is one that is not at all well understood, and also one which is currently the subject of much academic research. It is an example of Bare Coordination. This is when coordinated noun phrases (NPs) which we would otherwise expect to take a determiner of some description appear "bare" with no determiner or article at all. By coordinated, we mean that they appear in phrases using the coordinators and, or, but and so forth (some people call coordinators coordinating conjunctions). The reason that they seem to be able to appear like this is because they are in such coordinations.
Here are some more examples:
- A black cat and a brown dog were fighting in the street. Cat and dog were equally filthy.
- Are you man or mouse?
- I had pen and paper ready to make notes.
- Mother and child were said to be recovering well.
- He appeared to be millionaire and homeless vagabond at the same time.
- Nothing is so sacred as love between husband and wife.
Bare Coordination versus Bare Role NPs
Notice that these aren't bare role NP's which specify a unique role. Bare role NPs can occur freely as Predicative Complements without a determiner. The nouns in these coordinations cannot appear bare when not in a coordination:
Bare role NP
- He was Managing Director at Boots.
- Who's going to be Best Man?
- We elected her treasurer.
Nouns from the Bare Coordinations
- *He was millionaire. (ungrammatical)
- *He used to be cat. (ungrammatical)
- *Are you mouse? (ungrammatical)
- *She was wife. (ungrammatical)
Notice as well that bare role NP's can only function as Predicative Complements. However, bare co-ordinations can appear freely in Subject or Object function:
- Father and son came to see me. (Subject)
- We punished licensee and client together for the misdemeanour. (Direct Object)
Bare Role NP
- *Chief executive was an arse. (Subject, ungrammatical)
- *I punched Managing Director. (Object, ungrammatical)
Notice as well from the first group of examples, that it makes no difference whether the noun phrases are semantically definite or indefinite. In man or mouse both man and mouse are generic and don't refer to a or the man, or the mouse. In contrast, in Both husband and wife are recovering well, the husband and the wife are very specific, definite people. The fact that a noun phrase is in a bare coordination construction doesn't seem to depend on whether they are semantically definite or indefinite. Nobody knows why these bare noun phrases can occur in these coordinations. There is so much that we still don't know about language. Intriguing, isn't it!
Here's a couple of articles on bare coordination: