“Not” vs “and not”

Question

In general, when should I use "not" as opposed to "and not"? For example consider the following conversation:

A: Our price for the software is 50$ per user.
B: Our license for the server is per number of processors, and not per number of users. Therefore we prefer to license your software also per number of processors, and not per number of users. Do you have any such offerings?

Is it correct to use "and not" in the above sentences? Is it better to replace "and not" by just "not" ?

Answer 1

"X, not Y", "X, and not Y", and "not Y, but X" are all roughly synonymous, and largely interchangeable, but I think they have slightly different nuances:

• "X, not Y" tends to imply that X and Y are clear opposites; it suggests almost that "X" is equivalent to "not Y":
  • "I did it because I wanted to, not because I had to."
  • "I did it because I wanted to, not because he wanted me to."
  • "I did it because I wanted to, not in spite of wanting to." (Granted, it's hard to think of a context where one would need to utter this sentence.)
• "X, and not Y" tends to be used when the contrast is less direct, or the structures are less parallel:
  • "I did it because I wanted to, and not because I couldn't think of anything else to do."
  • "I did it because I wanted to, and not in expectation of some reward."
• "not Y, but X" is a bit literary or stylized. It tends to be used when X is perhaps surprising:
  • "I did it, not out of anxiety or panic or doubt, but because I actually wanted to."

In your example, I think bare "not" sounds best, but any of the three would work.

Answer 2

It would not make it better or worse, really. It might it sound "smoother" or maybe more tactful (slightly more polite, instead of contradictory). Usually, "and not" in this vendor-customer context sounds more helpful:

"We like apples, and not so much oranges" or "...and not oranges"

....sounds more polite than.....

"We like apples, but not oranges."

The latter seems more blunt, less graceful. Off the top of my head, I can't think of a specific situation in which using "not" or "and not" would make any difference. They sound virtually the same, though in a written form, one sounds slightly more tactful.

Answer 3

The example you gave is a little confusing for the following reasons:

1. "depends on the number"/ "(not) by the number" instead of "per number"
2. Second sentence and first sentence say the same thing but contradict each other on what is true (rule vs policy). Remove one of the two sentences.

Do not use "and" if you start a sentence. Do not use a comma if that is the last statement you are concatenating.

Here is one example.

Our license depends on the number of processors and not on the number of users. Do you have any such offerings?

Another Example.

We prefer to license your software by the number of processors. Our policy does not allow to license by the number of users. Do you have any such offerings?

If you need to have more than one concatenated element in your sentence, you should group all the elements with "not". If the sentence becomes too long, it is always better to break it down into smaller sentences.

Our license depends on the number of processors, hard drives, memories and not on the number of users, managers, developers. Do you have any such offerings?

I have to add: it makes a difference if you have a second verb or not.

Notice that in the sentence you gave, there is only one verb:

Our license for the server depends on the number of processors and not on the number of users.

In this case, it makes more sense to use and because both share the same verb.

However, if you had a different sentence like this

Our license for the server is usually discounted by the number of processors - not that we cannot do the same by the number of users.

then it makes more sense to not use and in the above sentence as each element is dependent on a different verb.