Part-of-speech tags: English

1 CCCoordinating conjunction
2 CDCardinal number
3 DTDeterminer
4 EXExistential there
5 FWForeign word
6 INPreposition or subordinating conjunction
7 JJAdjective
8 JJRAdjective, comparative
9 JJSAdjective, superlative
10 LSList item marker
11 MDModal
12 NNNoun, singular or mass
13 NNSNoun, plural
14 NPProper noun, singular
15 NPSProper noun, plural
16 PDTPredeterminer
17 POSPossessive ending
18 PPPersonal pronoun
19 PP$ Possessive pronoun
20 RBAdverb
21 RBRAdverb, comparative
22 RBSAdverb, superlative
23 RPParticle
24 SYMSymbol
25 TOto
26 UHInterjection
27 VBVerb, base form
28 VBDVerb, past tense
29 VBGVerb, gerund or present participle
30 VBNVerb, past participle
31 VBPVerb, non-3rd person singular present
32 VBZVerb, 3rd person singular present
33 WDTWh-determiner
34 WPWh-pronoun
35 WP$ Possessive wh-pronoun
36 WRBWh-adverb

More info: http://www.cis.uni-muenchen.de/~schmid/tools/TreeTagger/data/Penn-Treebank-Tagset.pdf