What is the difference between commentor and commentator? Is commentor or commenter a legitimate English word?
I do see the word "commenter" (but not "commentor") being used on Reddit, blogs, or actually right here on Stack Exchange. Others have pointed out that it seems to be an online thing, and I agree.
However, I disagree with the people saying that "commentator" sounds like someone who comments on sports. There are, for example, political commentators.
Back to Merriam-Webster, my understanding is that they are usually not too slow to catch up with the latest trends. They have a special section "New Words & Slang", a collection of user-submitted words. There you can find, for example, not one but five proposed meanings of the verb "to facebook". However, even that dedicated section doesn't mention "commenter", although blogs and online forums predate Facebook.
All that being said, there is no question that morphologically, "commenter" makes perfect sense. A killer is someone who kills, a driver is someone who drives, and a commenter is someone who comments. The "-er" is a so-called agent noun suffix, and it is very common in English.
On the other hand, the agent noun suffix "-or", while it does exist, is not common at all. Wiktionary lists as few as twelve terms that were derived using this suffix, and offers the following usage notes:
English generally appends this suffix where Latin would do it—to the root of a Latin-type perfect passive participle. For other words, English tends to use the suffix -er. Occasionally both are used (computer vs. computor).
Depending on where you live, you may have never encountered the word "computor" at all. However, I bet you have seen the word "computer" many times.
The bottom line:
- The word "commenter" is pretty common online, so if you use it, people should understand you. In formal writing, you might wish to use "commentator" instead.
- If you want to be on the safe side, you probably should not use "commentor" at all, though nobody can forbid you to do so.
Of course, the English language is constantly evolving, so both of the above recommendations may become obsolete as time passes.
The Oxford Living Dictionaries reports the following meaning of commentator.
- a person who comments on events or on a text.
- a person who delivers a live commentary on an event or performance.
For commenter, it says:
A person who expresses an opinion or engages in discussion of an issue or event, especially online in response to an article or blog post.
The given examples are the following ones.
The first commenter suggested that the story is a hoax.
a regular commenter on many blogs
Differently from the NOAD I had available in the Dictionary application on my Mac Mini, where commenter was just said to be a noun, the online dictionary makes clear that commentator is especially used for live commentary, while commenter is especially used for online comments to articles or blog posts.
The Corpus of Contemporary American English reports that commenter has been used between 2005–2010 more than the previous years (a ratio of 10:1). The word is used more on newspapers, and magazines, where it is used in sentences like
There is no humanity reading a book on a computer," wrote an anonymous commenter on the popular site ParentDish.com.
Even in academic context, the word is used with reference to who comments on a website.
[…] a school-board member in his home state of Nevada, from Charles Krauthammer to a commenter on a blog or a caller to a radio show.
My own feeling is that commenter is a new word used to mean the people who make comments on internet blogs, forums, etc. If you say someone is a commentator, it sounds like they are the person who comments on sports games as you watch them on the television, hence the necessity for the new word. However, strictly speaking, the person who writes comments on blogs is actually a commentator.
The OED’s entry for ‘commenter / ’commentor’, in the sense ‘one who comments; a commentator’, describes it as obsolete, but that clearly takes no account of its use on the internet. It isn’t new. The earliest citation is some time before 1387 and there are subsequent citations from Donne and Coleridge.
A commentator commentates events (like sport games on radio and TV) according to attributed time slot. That's why he has to fill with words the pauses in games, events, etc.
A commenter, on the contrary, comments. He is not obliged to maintain a word flow. Even more, he would be most probably banned as spammer for for commenting in order to fill the gaps in conversation.