Grammar
The method of writing is how you write. You can have vocabulary words, but you have to be able to put them together using some kind of method. This method happens to be grammar.
ぶんぽう
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. The ほう changes to ぽう.
日本語の文法の本をさがしています。
I'm looking for a Japanese grammar book.
文法を学べば学ぶほど、文章をかくのが上手になりますよ。
The more grammar you learn, the better your writing will become.
私の上司、見た目はできる男なのに、いつも間違った文法を使うのが残念すぎるよ。
My boss looks like a smart person, so it’s too bad that he always makes grammar mistakes.