Forum: ell.stackexchange.com
Tags: <word-choice><negation>
Title: Should I say: She is 'no' student or She is 'not' a student?
Question: I'm always confused with that issue. Should I say    She is  no  student   or    She is  not  a student   Or are  both of them  equal? If they are, what is the difference between them?

Answers:
sents: text: You can say either one, but they have different effects.
text: "She is not a student" is a simple statement of fact.
text: "She is no student" is usually an emphatic statement, which only really makes sense when you're denying somebody else's implication that she's a student.
text: For example, if one professor says, "A student asked me a question about [some crackpot theory] after yesterday's lecture," another professor might say, "She's no student!
text: She's just some woman who slips into lectures so she can ask her crazy questions."
text: You could also use it figuratively, to mean that she's such a bad student that she doesn't deserve the name: "Mary?
text: Ha!
text: She's no student.
text: I mean, she pays her fees and comes to lectures but have you ever seen her actually study anything?
text: I haven't!"
answer_details: author: ell.stackexchange.com/users/4468/David Richerby
score: 53
sents: text: You can say "She is no student."
text: This "style" is usually used for emphasis.
text: She is no student!
text: She's an imposter, just a journalist trying to get her story!"
text: You cannot say "She is not student".
text: Here you need an article.
text: Your edit makes your example correct.
text: She is not a student.
answer_details: author: ell.stackexchange.com/users/2704/James Webster
score: 18
sents: text: The first sentence can mean that she is not a student despite seeming like one.
text: Or that she did a bad job at being a student.
text: This is a bit of a strong statement.
text: The second sentence is not grammatical.
text: It should be
text: She is not a student.
text: The meaning of this sentence is self-explanatory.
text: To sum up, the two sentences do not mean identical things.
answer_details: author: ell.stackexchange.com/users/25052/Nihilist_Frost
score: 9
sents: text: The two statements have very different connotations.
text: "She is not a student" simply means what it says: "she is not a student, she is employed as a cleaner".
text: While "She is no student" probably means something like "She might be registered as a student, but she's making no effort to study"
answer_details: author: ell.stackexchange.com/users/9574/Michael Kay
score: 6
sents: text: I am an educated native speaker of American English.
text: In both British English and American English, I believe, "She is no student" is usually a flippant judgment, while "She is not a student" does not imply any moral judgment, unless the judgment is implied by tone of voice.
answer_details: author: ell.stackexchange.com/users/25621/John Hickey
score: 2
sents: text: "She is not a student" is just a statement, stating that she is not a student at all.
text: "She is no student" can mean different things, and is more empathic .
text: "She is no student" can mean that she does not study at all, she does not participate in projects, or even she does not even go to the school.
text: It can generally mean "She does not act like a student" or "She is not a student".
text: Examples: She
text: neither studies nor she does her homework.
text: She is no student!
text: or She hasn't ever written an essay, so she is no student.
text: But you can't say:
text: She hasn't ever written an essay, so she is not a student.
answer_details: author: ell.stackexchange.com/users/10658/EKons
score: 1

Summary of the answers:
The two sentences  do not  mean the same thing. "She is not a student" is a simple statement of fact.  However, "She is no student" would imply that although she may well be a student, she's making no effort to study, for example.  
The two sentences have different connotations. 'She is not a student' is a factual statement, 'she is no student' is a flippant value judgement.