write to (someone or something)
1. To send some written correspondence, such as a letter or email, to someone or some organization. A noun or pronoun can be used between "write" and "to" to specify the kind of written correspondence. She wrote a strongly worded letter to the airline to complain about the long delays on her flight. I'll have to write to your parents to let them know what happened.
2. To write something that acts as a part of or supplement to a different or larger piece of writing. A noun or pronoun is used between "write" and "to." My editor asked me to write an appendix to my latest book to help explain some of the more complicated historical details. She is currently writing a companion piece to her bestselling novel.
3. To send someone a written correspondence in order to communicate something specific. A noun or pronoun can be used between "write" and "to." I'm writing you to explain my absence from the meeting yesterday. The bank wrote to tell me that my account had had some suspicious activity recently.
write something to someone
1. to send specific information to someone in writing. I wrote the facts to John, and he thanked me for the information. They wrote all the details to me, and I filed them.
2. to compose a letter or e-mail and send it to someone. Sam wrote a letter to his father. Did you write that memo to Mark yet?
write something to something
to write something that is supplementary to something else. Molly wrote an epilogue to her story covering the time up till now. I will write the introduction to the book this afternoon.
write to someone
to compose a letter or e-mail and send it to someone. I will write to her again, but I don't expect to hear anything. Please write to me as soon as you can.