Extracted from the BNC Manual

AJ0
adjective (general or positive) e.g. good, old
AJC
comparative adjective e.g. better, older
AJS
superlative adjective, e.g. best, oldest
AT0
article, e.g. the, a, an, no . Note the inclusion of no: articles are defined as determiners which typically begin a noun phrase but cannot appear as its head.
AV0
adverb (general, not sub-classified as AVP or AVQ), e.g. often, well, longer, furthest. Note that adverbs, unlike adjectives, are not tagged as positive, comparative, or superlative. This is because of the relative rarity of comparative or superlative forms.
AVP
adverb particle, e.g. up, off, out. This tag is used for all prepositional adverbs, whether or not they are used idiomatically in phrasal verbs such as Come out here, or I can’t hold out any longer.
AVQ
wh-adverb, e.g. when, how, why. The same tag is used whether the word is used interrogatively or to introduce a relative clause.
CJC
coordinating conjunction, e.g. and, or, but.
CJS
subordinating conjunction, e.g. although, when.
CJT
the subordinating conjunction that, when introducing a relative clause, as in the day that follows Christmas. Some theories treat that here as a relative pronoun; others as a conjunction. We have adopted the latter analysis.
CRD
cardinal numeral, e.g. one, 3, fifty-five, 6609.
DPS
possessive determiner form, e.g. your, their, his.
DT0
general determiner: a determiner which is not a DTQ e.g. this both in This is my house and This house is mine. A determiner is defined as a word which typically occurs either as the first word in a noun phrase, or as the head of a noun phrase.
DTQ
wh-determiner, e.g. which, what, whose, which. The same tag is used whether the word is used interrogatively or to introduce a relative clause.
EX0
existential there, the word thereappearing in the constructions there is…, there are ….
ITJ
interjection or other isolate, e.g. oh, yes, mhm, wow.
NN0
common noun, neutral for number, e.g. aircraft, data, committee. Singular collective nouns such as committee take this tag on the grounds that they can be followed by either a singular or a plural verb.
NN1
singular common noun, e.g. pencil, goose, time, revelation.
NN2
plural common noun, e.g. pencils, geese, times, revelations.
NP0
proper noun, e.g. London, Michael, Mars, IBM. Note that no distinction is made for number in the case of proper nouns, since plural proper names are a comparative rarity.
ORD
ordinal numeral, e.g. first, sixth, 77th, next, last. No distinction is made between ordinals used in nominal and adverbial roles. next and last are included in this category, as general ordinals.
PNI
indefinite pronoun, e.g. none, everything, one (pronoun), nobody. This tag is applied to words which always function as heads of noun phrases. Words like some and these, which can also occur before a noun head in an article-like function, are tagged as determiners, DT0 or AT0.
PNP
personal pronoun, e.g. I, you, them, ours. Note that possessive pronouns such as ours and theirs are included in this category.
PNQ
wh-pronoun, e.g. who, whoever, whom. The same tag is used whether the word is used interrogatively or to introduce a relative clause.
PNX
reflexive pronoun, e.g. myself, yourself, itself, ourselves.
POS
the possessive or genitive marker ‘s or ‘. Note that this marker is tagged as a distinct word. For example, Peter’s or someone else’s is tagged <EG><![CDATA [ <w NP0>Peter<W POS>’s <W CJC>or <W PNI>someone <W AV0>else<W POS>’s ]]> </EG>
PRF
the preposition of. This word has a special tag of its own, because of its high frequency and its almost exclusively postnominal function.
PRP
preposition, other than of, e.g. about, at, in, on behalf of, with. Note that prepositional phrases like on behalf of or in spite of are treated as single words.
TO0
the infinitive marker to.
UNC
unclassified items which are not appropriately classified as items of the English lexicon. Examples include foreign (non-English) words; special typographical symbols; formulae; hesitation fillers such as errm in spoken language.
VBB
the present tense forms of the verb be, except for is or ‘s am, are ‘m, ‘re, be (subjunctive or imperative), ai (as in ain’t).
VBD
the past tense forms of the verb be, was, were.
VBG
-ing form of the verb be, being.
VBI
the infinitive form of the verb be, be.
VBN
the past participle form of the verb be, been
VBZ
the -s form of the verb be, is, ‘s.
VDB
the finite base form of the verb do, do.
VDD
the past tense form of the verb do, did.
VDG
the -ing form of the verb do, doing.
VDI
the infinitive form of the verb do, do.
VDN
the past participle form of the verb do, done.
VDZ
the -s form of the verb do, does.
VHB
the finite base form of the verb have, have, ‘ve.
VHD
the past tense form of the verb have, had, ‘d.
VHG
the -ing form of the verb have, having.
VHI
the infinitive form of the verb have, have.
VHN
the past participle form of the verb have, had.
VHZ
the -s form of the verb have, has, ‘s.
VM0
modal auxiliary verb, e.g. can, could, will, ‘ll, ‘d, wo (as in won’t)
VVB
the finite base form of lexical verbs, e.g. forget, send, live, return. This tag is used for imperatives and the present subjunctive forms, but not for the infinitive (VVI).
VVD
the past tense form of lexical verbs, e.g. forgot, sent, lived, returned.
VVG
the -ing form of lexical verbs, e.g. forgetting, sending, living, returning.
VVI
the infinitive form of lexical verbs , e.g. forget, send, live, return.
VVN
the past participle form of lexical verbs, e.g. forgotten, sent, lived, returned.
VVZ
the -s form of lexical verbs, e.g. forgets, sends, lives, returns.
XX0
the negative particle not or n’t.
ZZ0
alphabetical symbols, e.g. A, a, B, b, c, d.

The following portmanteau tags are used to indicate where the CLAWS system has indicated an uncertainty between two possible analyses:

AJ0-AV0
adjective or adverb
AJ0-NN1
adjective or singular common noun
AJ0-VVD
adjective or past tense verb
AJ0-VVG
adjective or -ing form of the verb
AJ0-VVN
adjective or past participle
AVP-PRP
adverb particle or preposition
AVQ-CJS
wh-adverb or subordinating conjunction
CJS-PRP
subordinating conjunction or preposition
CJT-DT0
that as conjunction or determiner
CRD-PNI
one as number or pronoun
NN1-NP0
singular common noun or proper noun
NN1-VVB
singular common noun or base verb form
NN1-VVG
singular common noun or -ing form of the verb
NN2-VVZ
plural noun or -s form of lexical verb
VVD-VVN
past tense verb or past participle

The following codes are used with c elements only:

PUL
left bracket (i.e. ( or [ )
PUN
any mark of separation ( . ! , : ; – ? … )
PUQ
quotation mark ( ' ` )
PUR
right bracket (i.e. ) or ] )

Note that some punctuation marks (notably long dashes and ellipses) are not tagged as such in the corpus, but appear simply as entity references.