Home

The LDC Catalog features classic corpora responsible for critical advances in human language technology that continue to influence researchers. Among them are the Penn Treebank releases, Treebank-2 (LDC96T7) and Treebank-3 (LDC99T42). 

The Penn Treebank project (1989-1996) produced seven million words tagged for part-of-speech, three million words of parsed text, over two million words annotated for predicate-argument structure and 1.6 million words of transcribed speech annotated for speech disfluencies (Taylor et al., 2003). Source material represents a diverse range of data, including Wall Street Journal (WSJ) articles, the Brown Corpus and Switchboard telephone conversations. 

Penn Treebanks are used for a wide range of purposes, including the creation and training of parsers and taggers, work on machine translation and speech recognition, and research concerning joint syntactic and semantic role labeling. Their ongoing influence is evidenced by the popularity of Treebank-3 (LDC99T42), which continues to be one of LDC’s top ten most distributed corpora in the Catalog. In addition, the WSJ section has served as a model for treebanks across many languages (Nivre, 2008).

The Penn Treebank has inspired related annotation schemes, such as Proposition Bank, the Penn Discourse Treebank project, and word alignment annotation. In addition, LDC has developed revised English treebank guidelines resulting in the re-issue of the WSJ section (English News Text Treebank: Penn Treebank Revised (LDC2015T13)) and treebanked web text (e.g., English Web Treebank (LDC2012T13) and BOLT English Translation Treebank – Chinese Discussion Forum (LDC2020T09)).   

Penn Treebank corpora and its related releases are available for licensing to LDC members and nonmembers. For more information about licensing LDC data, visit Obtaining Data.