[contribution pages] change 'confirm contribution' button text

As a civicrm user
I need to modify the text of the contribution page(s) 'confirm contribution' button
so that I can taylor the verbage to my specific organization

E.g. we are using contribution pages to manage memberships for an online magazine subscription. When the user sees the 'confirm contribution' text, they may be slightly confused, as they are in the context of 'subscribing to magazine'.