Chinese Language Stack Exchange is a question and answer site for students, teachers, and linguists wanting to discuss the finer points of the Chinese language. It only takes a minute to sign up.
Sign up to join this community
For context, this is from lesson eight of Integrated Chinese.
I know 李友的 means "Li You's" and 一篇日记 is "a/one dictionary", but 李友的一篇日记 together doesn't make sense to me.
Is it just a casual usage of a counter, or does it mean something like "an entry/article from Li You's diary"?
李友的一篇日记
You already know the first portion, lets break down the rest.
一篇 measure word for in this case a piece of writing/article etc.
日记 I understand the confusion but this term does not mean diary. it is an entry in a daily log. In this case the entry is a diary section, but the same term could be used for tracking repeating events daily, or scientific experiment recording, and so on.
That said, because there is no plural in Chinese, referring to the full collection of all entries is also 日记.
As long as you treat it like any other noun in that sense you should avoid confusion: remember that it usually defaults to the singular (entry here), unless context or additional words (like 本、簿、賬 here) say otherwise. The use of 一 with the measure word is also helpful context of it being singular.
In a diary, the topic and contents change every day, you won't quote the entire diary but a piece of it. This piece usually contains, and conveys a meaningful story/event that equates to 一篇文章 (a short article, or an essay, on a book, magazine, or diary). 李友的一篇日记 indicates "an article/essay originated from 李友's dairy".
The answer of your question is: 李友的一篇日记 means a piece of 李友's diary of a certain day. In Chinese, if only refers 日记 without any count, it is plural 日记 which has almost the same meaning with English: "a book in which you can write down the experiences you have each day, your private thoughts, etc." (from Oxford dictionary). If there is a count in front like "一篇日记"， the "日记" here after the "一篇" means a piece of the diary of a certain day.
By the way, 日记 is not equal to "diary". Diary means all the 日记 of a people, whereas 日记 means a piece of diary of a certain day. You can treat diary as plural of 日记. Most Chinese words have no plural conversions, but if do, you can treat "diary" as "日记s" (no such usage, just for understanding).
李友的一篇日记：an entry from Li You’s journal.
The main difference between journal and diary is that a journal is a personal record where you can pen your thoughts, observations, and experiences, while a diary is a book where you note down important things to keep track of them. Journals and diaries are books where you can keep a record of events and experiences.
So the longer and more detailed is the piece of writing when “thoughts,observations and experiences” are included, the more likely it would be a journal entry rather than a diary entry, the main purpose of which would be to “keep track of events”.
Looks like he is a serial diary writer:
李友的一篇日记
One of Li You's diaries
