||This article needs additional citations for verification. (December 2006)|
A question tag or tag question is a grammatical structure in which a declarative statement or an imperative is turned into a question by adding an interrogative fragment (the "tag"). For example, in the sentence "You're John, aren't you?", the statement "You're John" is turned into a question by the tag "aren't you". The term "question tag" is generally preferred by British grammarians, while their American counterparts prefer "tag question".
In most languages, tag questions are more common in colloquial spoken usage than in formal written usage. They can be an indicator of politeness, emphasis or irony. They may suggest confidence or lack of confidence; they may be confrontational, defensive or tentative. Although they have the grammatical form of a question, they may differ from questions in that they do not expect an answer. In other cases, when they do expect a response, they may differ from straightforward questions in that they cue the listener as to what response is desired. In legal settings, tag questions can often be found in a leading question. According to a specialist children's lawyer at the NSPCC, children find it difficult to answer tag questions other than in accordance with the expectation of questioner.
Question tags are formed in several ways, and many languages give a choice of formation. In some languages the most common is a single word or fixed phrase, whereas in others it is formed by a regular grammatical construction.
Single word forms 
In many languages, the question tag is a simple positive or negative. Russian allows да?, yes?, whereas Spanish and Italian use ¿no? and no? respectively.
Another common formation is equivalent to the English correct? or the informal form right?. This more often is realised as the word for true or truth, such as in Polish prawda?, or Spanish ¿verdad?, which in turn can be presented in a negative form, such as in the Polish nieprawdaż?, German nicht wahr? (not true?) or Lithuanian "ar ne?". Alternatively, a word or short phrase indicating agreement can be used, such as the French d'accord?. However, the equivalent in many languages is not a true tag question, but rather a complete question.
A plain conjunction may be used, such as the Czech že? (that).
Various other words occur in specific languages, such as German oder? (or).
Finally, some languages have words whose only function is as a question tag. In Scots and certain dialects of English, eh? functions this way. French has hein?, Southern German dialects have gell? and Portuguese has né? (actually a colloquial contraction of não é?, literally isn't it?, while é?, pronounced much like English eh?, would have a different intended meaning, that of English right?).
Grammatically regular forms 
In several languages, the tag question is built around the standard interrogative form. In English and the Celtic languages, this interrogative agrees with the verb in the main clause, whereas in other languages the structure has fossilised into a fixed form.
Grammatically productive tag forms 
Grammatically productive tag forms are formed in the same way as simple questions, referring back to the verb in the main clause and agreeing in time and person (where the language has such agreement. The tag may include a pronoun, such as in English, or may not, as is the case in Scottish Gaelic. If the rules of forming interrogatives require it, the verb in the tag may be an auxiliary, as in English.
Tag questions in English 
English tag questions, when they have the grammatical form of a question, are atypically complex, because they vary according to four factors: the choice of auxiliary, the negation, the intonation pattern and the emphasis.
The English tag question is made up of an auxiliary verb and a pronoun. The auxiliary has to agree with the tense, aspect and modality of the verb in the preceding sentence. If the verb is in the present perfect, for example, the tag question uses has or have; if the verb is in a present progressive form, the tag is formed with am, are, is; if the verb is in a tense which does not normally use an auxiliary, like the present simple, the auxiliary is taken from the emphatic do form; and if the sentence has a modal auxiliary, this is echoed in the tag:
- He's read this book, hasn't he?
- He read this book, didn't he?
- He's reading this book, isn't he?
- He reads a lot of books, doesn't he?
- He'll read this book, won't he?
- He should read this book, shouldn't he?
- He can read this book, can't he?
A special case occurs when the main verb is to be in a simple tense. Here the tag question repeats the main verb, not an auxiliary:
- This is a book, isn't it?
(Not doesn't it?, as the normal rules for present simple would suggest.)
If the main verb is to have, either solution is possible:
- He has a book, hasn't he?
- He has a book, doesn't he?
English tag questions may contain a negation, but need not. When there is no special emphasis, the rule of thumb often applies that a positive sentence has a negative tag and vice versa. This form usually seeks confirmation of the asker's opinion or belief.
- She is French, isn't she?
- She's not French, is she?
These are sometimes called "balanced tag questions". However, it has been estimated that in normal conversation, as many as 40%-50% of tags break this rule. "Unbalanced tag questions" (positive to positive or negative to negative) may be used for ironic or confrontational effects:
- Do listen, will you?
- Oh, I'm lazy, am I?
- Jack: I refuse to spend Sunday at your mother's house! Jill: Oh you do, do you? We'll see about that!
- Jack: I just won't go back! Jill: Oh you won't, won't you?
Patterns of negation can show regional variations. In North East Scotland, for example, positive to positive is used when no special effect is desired:
- This pizza's fine, is it? (standard English: This pizza's delicious, isn't it?)
Note the following variations in the negation when the auxiliary is the I form of the copula:
- England (and America, Australia, etc.): Clever, aren't I?
- Scotland/Northern Ireland: Clever, amn't I?
- nonstandard dialects: Clever, ain't I?
English tag questions can have a rising or a falling intonation pattern. This can be contrasted with Polish, French or German, for example, where all tags rise, or with the Celtic languages, where all fall. As a rule, the English rising pattern is used when soliciting information or motivating an action, that is, when some sort of response is required. Since normal English yes/no questions have rising patterns (e.g. Are you coming?), these tags make a grammatical statement into a real question:
- You're coming, aren't you?
- Do listen, will you?
- Let's have a beer, shall we?
The falling pattern is used to underline a statement. The statement itself ends with a falling pattern, and the tag sounds like an echo, strengthening the pattern. Most English tag questions have this falling pattern.
- He doesn't know what he's doing, does he?
- This is really boring, isn't it?
Sometimes the rising tag goes with the positive to positive pattern to create a confrontational effect:
- He was the best in the class, was he? (rising: the speaker is challenging this thesis, or perhaps expressing surprised interest)
- He was the best in the class, wasn't he? (falling: the speaker holds this opinion)
- Be careful, will you? (rising: expresses irritation)
- Take care, won't you? (falling: expresses concern)
Sometimes the same words may have different patterns depending on the situation or implication.
- You don't remember my name, do you? (rising: expresses surprise)
- You don't remember my name, do you? (falling: expresses amusement or resignation)
- Your name's Mary, isn't it? (rising: expresses uncertainty)
- Your name's Mary, isn't it? (falling: expresses confidence)
It is interesting that as an all-purpose tag the Multicultural London English set-phrase innit (for "isn't it") is only used with falling patterns:
- He doesn't know what he's doing, innit?
- He was the best in the class, innit?
On the other hand, the adverbial tag questions (alright? OK? etc.) are almost always found with rising patterns. An occasional exception is surely.
Variant forms 
There are a number of variant forms that exist in particular dialects of English. These are generally invariant, regardless of verb, person or negativity.
The tag eh? is of Scottish origin, and can be heard across much of Scotland, New Zealand, Canada and the North-Eastern United States. In Central Scotland (in and around Stirling and Falkirk), this exists in the form eh no? which is again invariant.
False tag in Welsh English 
It is often erroneously assumed that Welsh speakers of English use a tag question to make an emphatic statement, e.g.: Lovely day, isn't it?
However, this is instead a cleft sentence of the form: Lovely day, is in it.
This has its roots in the Welsh language, and this type of cleft features in all extant Celtic languages. The lack of verb at the start of this construction coupled with the lack of rising intonation mark this as distinct from tag questions, which are used in Welsh English in the same manner as the majority of the UK.
Tag questions in the Celtic languages 
Like English, the Celtic languages form tag questions by echoing the verb of the main sentence. The Goidelic languages, however, make little or no use of auxiliary verbs, so that it is generally the main verb itself which reappears in the tag. As in English, the tendency is to have a negative tag after a positive sentence and vice versa, but unbalanced tags are also possible. Some examples from Scottish Gaelic:
(Here, eil and fhaca are dependent forms of the irregular verbs tha and chunnaic.)
- Is toil leat fìon, nach toil? - You like wine, don't you?
- Tha i brèagha an diugh, nach eil? - It's nice today, isn't it?
- Chunnaic mi e, nach fhaca? - I saw him, didn't I?
- Thèid mi ga dhùsgadh, an tèid? - I'll go and wake him, shall I? (unbalanced!)
In Welsh, a special particle is used to mark tag questions, which are then followed by the inflected form of a verb. With the auxiliary bod, it is the inflected form of bod that is used:
- Mae hi'n bwrw glaw heddiw, on'd ydy? - It's raining today, isn't it?
With inflected non-preterite forms, the inflected form of the verb is used:
- Doi di yfory, on' doi? - You'll come tomorrow, won't you?
With preterite and perfect forms, the invariable do (also the affirmative answer to these questions) is used:
- Canodd y bobl, on' do? - The people sang, didn't they?
- Mae hi wedi ei weld o, on'do? - She's seen him, hasn't she?
When a non-verbal element is being questioned, the question particle ai is used:
- Mr Jones, on'dai? - Mr Jones, isn't it?