TreeTagger is widely used for part-of-speech (pos) tagging but some of the well known language processing tools like Malt Parser require corpus tagged with Penn Treebank (PTB) tagset. Though TreeTagger uses PTB tagset there are some major differences (I believe TreeTagger tagset is more expressive than the PTB). But it is fairly straightforward to convert TreeTagger tags to PTB tags (but not the other way). The table below maps TreeTagger tags to PTB tags.

TreeTagger PTB Tagset
NP
NNP
NPS
NNPS
VH
VB
VHD
VBD
VHG
VBG
VHN
VBN
VHP
VBP
VHZ
VBZ
VV
VB
VVD
VBD
VVG
VBG
VVN
VBN
VVP
VBP
VVZ
VBZ
IN/that
IN
PP
PRP
PP$
PRP$
SENT
See Below
Mapping of TreeTagger Tags to Penn Treebank Tagset

NB: There are some differences in punctuations tags especially the sentence end markers. PTB tagset has no sentence end markers, so just replace any sentence end marker with the punctuation word itself.

Useful links:

TreeTagger Tagset: http://courses.washington.edu/hypertxt/csar-v02/penntable.html

Other Versions of TreeTagger Tagset: http://trac.sketchengine.co.uk/wiki/tagsets/penn

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