User:SOTO/Forum Archive/The Reference Desk/@comment-24894325-20160309221053/@comment-188432-20160804174551

Scripts should never be used to determine spelling of ordinary English words. They are typically written under tremendous pressure of time, and mistakes are highly likely. It's definitely vitreous.

(In fact the vitreous nature of time is graphically shown to us in the series 2 finale, where Ten breaks glass in Torchwood London to show how easy it is to screw up time. This, um, shattering event would have likely been fresh in the minds of the writers of 2009's Mary's Story, since we know BF plays are typically produced at least a year before they're released.)