Similarly to the SUSANNE Corpus Tagset, the Penn Treebank Tagset consists of two main parts. There is the syntactic tagset and the POS tagset.
The syntactic tagset
| ADJP | Adjective phrase |
| ADVP | Adverb phrase |
| NP | Noun phrase |
| PP | Prepositional phrase |
| S | Simple declarative clause |
| SBAR | Clause introduced by subordinating conjunction or 0 (see below) |
| SBARQ | Direct question introduced by wh-word or wh-phrase |
| SINV | Declarative sentence with subject-aux inversion |
| SQ | Subconstituent of SBARQ excluding wh-word or wh-phrase |
| VP | Verb phrase |
| WHADVP | Wh-adverb phrase |
| WHNP | Wh-noun phrase |
| WHPP | Wh-prepositional phrase |
| X | Constituent of unknown or uncertain category |
| Null elements | |
| * | „Understood“ subject of infinitive or imperative |
| 0 | Zero variant of that in subordinate clauses |
| T | Trace—marks position where moved wh-constituent is interpreted |
| NIL | Marks position where preposition is interpreted in pied-piping contexts |
The POS tagset
| CC | Coordinating Conjunction |
| CD | Cardinal Number |
| DT | Determiner |
| EX | Existential there |
| FW | Foreign word |
| IN | Preposition/subordinating conjunction |
| JJ | Adjective |
| JJR | Adjective, comparative |
| JJS | Adjective, superlative |
| LS | List item marker |
| MD | Modal |
| NN | Noun, singular or mass |
| NNS | Noun, plural |
| NNP | Proper noun, singular |
| NNPS | Proper noun, plural |
| PDT | Predeterminer |
| POS | Posessive ending |
| PRP | Personal pronoun |
| PP | Posseive pronoun |
| RB | Adverb |
| RBR | Adverb, comparative |
| RBS | Adverb, superlative |
| RP | Particle |
| SYM | Symbol (mathematic or scientific) |
| TO | to |
| UH | Interjection |
| VB | Verb, base form |
| VBD | Verb, past tense |
| VBG | Verb, gerund/present participle |
| VBN | Verb, past participle |
| VBP | Verb, non-3rd person singular present |
| VBZ | Verb, 3rd person singular present |
| WDT | wh-determiner |
| WP | wh-pronoun |
| WP$ | Possesive wh-pronoun |
| WRB | wh-adverb |
| # | Pound sign |
| $ | Dollar sign |
| . | Sentence-final punctuation |
| , | Comma |
| : | Colon, semi-colon |
| ( | Left bracket character |
| ) | Right bracket character |
| " | Straight double quote |
| ‘ | Left open single quote |
| “ | Left open double quote |
| ’ | Right closed single quote |
| ” | Right closed double quote |
This list is taken from the HTML version of ‚Building a large annotated corpus of English: the Penn Treebank‘ by Mitchell P. Marcus, Mary Ann Marcinkiewicz, Beatrice Santorini which also contains a lot of useful information about the Penn Treebank.