I have come across a syntax tree with a subordinate clause phrase (as opposed to just a sentence) whose left daughter is a verb in the imperative, e.g. Wash your laundry tonight.

I have read this post and also these resources which define a subordinate conjunction: 1, 2, and 3, but none of them said an imperative verb could be a subordinate conjunction.

Last, I also searched several thousand parsed trees but not a single left daughter was a verb to the subordinate clause phrase.

My conclusion is that it's a tagger mistake.

Edit: Here is the utterance for context

Review your homework for 30 minutes and make sure it is complete.

In the tree, review is assigned the part-of-speech label for a subordinating conjunction, being the left daughter to that subordinating clause.

  • 1
    Can you provide the whole sentence to give us some context?
    – robert
    Commented Nov 16, 2014 at 18:37
  • 2
    Probably it is a tagger mistake; somebody musta defined a subordinate clause as one lacking a subject NP. English speakers do use bald subordinate clauses as single utterances, after all.
    – jlawler
    Commented Nov 16, 2014 at 18:37
  • It's a tagger mistake. and isn't a subordinating conjunction, but rather we're dealing with coordination. Commented Nov 17, 2014 at 6:56
  • @ThomasGross I was not referring not to and but to review being labeled as a subordinating conjunction. Could you explain how a trained tagger could make this mistake (I would accept that as an answer)? I'm assuming the tagger is some kind of HMM/CRF trained on a lot of annotated data. How could it label a verb as IN if that never occurs in the training set? Commented Nov 17, 2014 at 20:58

1 Answer 1


As requested by user3898238 in his comment to mine, I try to provide an answer:
The verb review is, wrongly, labeled as a subordinating conjunction for the possible reason that in English conjunctions precede the clause they head. Since a subordinating conjunction is absent, the program simply chooses the next available option, i.e. the initial word.

My explanation for the program apparently seeing a subordinating structure, instead of a coordinating one, would be that the presence of the coordinating conjunction and forces a two-clause analysis. And many computer linguists (i.e. the people who build taggers, etc.) view coordination as akin to subordination (cf. the treatment of coordination in MTT).

According to my personal experience, computer "linguists" make terrible linguists.

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