Shield:

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The files in this repository contain mappings from treebank specific tagsets to a set of 12 universal part-of-speech tags. The 12 universal tags are:

VERB - verbs (all tenses and modes)
NOUN - nouns (common and proper)
PRON - pronouns 
ADJ - adjectives
ADV - adverbs
ADP - adpositions (prepositions and postpositions)
CONJ - conjunctions
DET - determiners
NUM - cardinal numbers
PRT - particles or other function words
X - other: foreign words, typos, abbreviations
. - punctuation

See "A Universal Part-of-Speech Tagset" by Slav Petrov, Dipanjan Das and Ryan McDonald for more details:

http://arxiv.org/abs/1104.2086