An adverbial complementizer is a morpheme that introduces a subordinate, adverbial clause.  In languages like English, these words occur at the beginning of the subordinate clause, as in <i>The dog barked <b>when</b> it heard a burglar</i>. This property refers only to non-affixal complementizers. See Dryer (2008) for discussion.

<br><br><b>Reference</b><br>
Dryer, Matthew S. 2008. Order of Adverbial Subordinator and Clause.
In Haspelmath et al. (2008), chapter 94.
Available online at <a href="http://wals.info/feature/94">http://wals.info/feature/94</a href>.

