- write something in
- write something into something & write something in†1. to write information into something. •
I wrote her telephone number into my notebook.
•I wrote in her number.
•I took out my notebook and wrote it in.
2. to include a specific statement or provision in a document, such as a contract or agreement. •I want you to write a stronger security clause into my contract.
•I will write in a stronger clause.
Dictionary of American idioms. 2013.