"I am writing in response to your mail."
What does it mean by "in" in this sentence?
Is "I am writing for response to your mail." acceptable?
In this scenario, response is referring to "a verbal or written answer" or, simply, "a reaction":
- a verbal or written answer: we received 400 applications in response to one job ad.
- a reaction to something: an honors degree course in Japanese has been established in response to an increasing demand.
The preposition in is therefore more suitable:
3. indicating a state, situation, or condition ⇒ in a deep sleep, standing in silence
If you are a native speaker of English or you've familiarized yourself with linguistic expressions in English (by reading many English books and listening to many English podcasts, etc), you can tell straight away that the expression writing for response simply makes no sense.
No, only in response is possible. Prepositions like in have many uses, and, if you are a foreign learner of English, the simplest course is to learn them as parts of complete phrases.
The correct phrase is the latter: in response to. Another very appropriate phrase would be in a response to. If you do not want to use the word “in”, consider using as a response to.