The Penn Treebank tagset.

     CC      Coordinating conjunction
     CD      Cardinal number
     DT      Determiner
     EX      Existential there
     FW      Foreign word
     IN      Preposition or subordinating conjunction
     JJ      Adjective
     JJR     Adjective, comparative
     JJS     Adjective, superlative
     LS      List item marker
     MD      Modal
     NN      Noun, singular or mass
     NNS     Noun, plural
     NP      Proper noun, singular
     NPS     Proper noun, plural
     PDT     Predeterminer
     POS     Possessive ending
     PP      Personal pronoun
     PP$     Possessive pronoun
     RB      Adverb
     RBR     Adverb, comparative
     RBS     Adverb, superlative
     RP      Particle
     SYM     Symbol
     TO      to
     UH      Interjection
     VB      Verb, base form
     VBD     Verb, past tense
     VBG     Verb, gerund or 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$     Possessive wh-pronoun
     WRB     Wh-adverb