How does using "not" differ from using a negative word?


How does using "not" differ from using a word with a negative prefix?

For example:

It's unwise to vote down this question.
It's not wise to vote down this question

I know semantically (or literally), they're the same. However, I want to know grammatically, how do they differ?


Posted 2015-06-04T16:34:47.997

Reputation: 1 054

1By "technically", do you mean that you want to know the grammatical terminology to describe the difference? – Ben Kovitz – 2015-06-04T17:12:16.073

Yes. according to the facts or exact meaning of something; strictly (from Google, 1st definition) – XPMai – 2015-06-04T17:23:45.537

2"Define technically" does not specifically mean "supply the grammatical terminology". "Technical" is actually a vague word in English, despite the fact that it suggests a kind of preciseness. Contrasting "semantically" with "technically" doesn't really make sense. A reader wonders, "What kind of preciseness do you have in mind?" BTW, referring someone to is a little bit insulting, as it suggests that I was careless and could easily have looked up the definition for myself. But if you look at the results, the definition doesn't mention grammatical terminology. – Ben Kovitz – 2015-06-04T17:33:20.783

Technically they differ because one uses the prefix "un-" and the other uses the word "not". I'm pretty sure that this is not the "technical" answer you want but it is a technical one. – Catija – 2015-06-04T17:38:55.460

1"Specifically" is not any better than "technically". You want "grammatically" – Catija – 2015-06-04T17:49:13.153

"Opionally"/commonly/regularly/usually/normally, if you asked a question that you've been thinking of it for so long, suddenly get a notification, open it and see criticisms of grammatical errors and accusations of offending someone instead of informative/helpful answers, how would you feel? Feel free to edit it if you think it's wrong but can still be understood by the public, since I've never proclaimed that I'm a professor. – XPMai – 2015-06-04T18:15:52.757

2Actually, in my first comment, I asked you for clarification. It was not a criticism. The clarification is needed to write a helpful answer. – Ben Kovitz – 2015-06-04T18:26:29.427

By the way, anyone who have voted down this question please tell me why it's low quality because I want to know. Thanks! – XPMai – 2015-06-04T20:59:27.093

I think it is now much improved with the change to grammatically. It was unclear what you wanted to know before. – Aaron Brown – 2015-06-04T23:17:27.213



Grammatically, unwise and not wise are nearly identical. Unwise is an adjective, while not wise is an adjective phrase.

To expand on the subject in general, you can add the prefix un- to many adjectives to form a negative form. Other examples are unclear, unaware, and unpleasant. Some words take a different prefix, such as il- in illegitimate (the opposite of legitimate), or dis- in dishonored, in which case the un- form does not exist or is very uncommon. Unfortunately most of these must be learned by rote (you have to memorize it for each word), as there isn't a good way to know without looking it up.

Aaron Brown

Posted 2015-06-04T16:34:47.997

Reputation: 1 547

Can you simplify this part, "To expand on the subject in general,", I don't understand what it means. – XPMai – 2015-06-05T14:34:04.137

@XPMai I tried to clarify a little bit. What do you not understand specifically? – Aaron Brown – 2015-06-05T22:50:43.073

I don't understand the connotation. How to expand a subject? What subject you referring? – XPMai – 2015-06-06T01:06:54.220

"To expand on a subject" means to explain more about a particular idea. The subject, or idea, that I am referring to is negative adjectives. – Aaron Brown – 2015-06-06T15:26:58.503


  1. It's unwise to vote down this question.
  2. It's not wise to vote down this question

Adding a prefix like un- to an adjective is grammatically very different from using the adverb not to negate a verb phrase. The most important difference is that using not makes the whole clause negative, whereas a clause containing an adjective with un- will be positive unless there is some other word that makes it negative.

One way that we can show this is to put a negative question tag onto the end of the clause. Usually, when the we have a positive clause we find a negative question tag. If we have a negative clause, we see a positive tag:

  • It's unwise to vote down this question, isn't it?
  • It's not wise to vote down this question, is it?

If we use the opposite tags the sentences will either be marked (have an unusual meaning), or be ungrammatical:

  • It's unwise to vote down this question, is it? (unusual/marked tag)
  • It's not wise to vote down this question, isn't it? (ungrammatical)

Another effect this has on the grammar is that there are words and phrases which we can use in negative clauses that won't work so well in positive ones. These are usually called negative polarity items. So there are words and phrases we can use with sentence (2) that we can't use with sentence (1). Take for example the negative polarity items either or at all:

  • *It's unwise to vote down this question either. (ungrammatical)
  • It's not wise to vote down this question either.
  • *It's unwise at all to vote down this question. (ungrammatical)
  • It's not wise at all to vote down this question.

So although the meaning of sentences (1) and (2) is very similar, the grammar is completely different!

Araucaria - Not here any more.

Posted 2015-06-04T16:34:47.997

Reputation: 25 536

I can feel those 2 are wrong, but if I were asked to explain why, I can't. Can you? | Tenses are correct; sentence structure is correct; punctuation are placed at the right positions. What else that makes the 2 sentences wrong? – XPMai – 2015-06-07T10:55:48.633