I want to talk about English grammar in technical terms. Example, I might want to discuss 文型:
Every English sentence must have a main verb.
I would say:
英文{えいぶん}では、文章{ぶんしょう}にいつも本動詞{ほんどうし}がついている。
To me, saying 文章 in that context sounds good, but the meaning is a little weird. I think of 文章 as really meaning "document(s)".
How should one say "a sentence" in the context of a technical discussion about English sentence structures.
Note. My dictionary defines 一文 as "a sentence", yet I've never heard a native say いちぶん. Though, my listening skills are not the best...