preparatory
adj.done in order to get ready for something more important that will happen later.
adj.serving to prepare for a subsequent event or action; introductory in nature.
“The team did some preparatory exercises before the big game.”
“The committee held several preparatory meetings to ensure the main conference would run smoothly next month.”
“Before the surgeon began the delicate procedure, the medical staff completed a series of preparatory checks to verify that all equipment was sterile and functioning correctly.”
Typically used attributively before a noun; often followed by the preposition 'to'.
When used to indicate what something is preparing for, the adjective takes the preposition 'to' rather than 'of'.
“The judge ruled that the operators could continue preparatory work at the sites but must stop short of producing oil and gas until a final decision had been taken.”
“The collection that Daniel holds is now fully digitized, and includes Ed’s finished paintings and works on paper, preparatory tracings, journals and sketchbooks.”
From Middle English preparatori, from Late Latin praeparatorius. By surface analysis, prepare + -atory.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.