preparatory school (for entrance examinations);  cram school;  cramming school
 background knowledge;  prerequisite knowledge
 reserves (esp. troops);  reserve army;  potential members of some group (e.g. the elderly);  people at risk (e.g. of a medical condition);  wannabees
 service in the first reserve
 preliminary election;  primary (election)
 reserve funds;  emergency funds
 preliminary investigation
 spade work;  preliminaries
 reserve equipment;  backup unit;  spare
 pilot study;  preliminary study
 crime of plotting a crime;  crime of preparing to commit an offense;  preparation of a crime
 reserve fund;  emergency fund
 voir dire (hearing to determine the admissibility of evidence, or the competency of a witness or juror)
 court of inquiry;  court of enquiry
 (crime of) preparations or plots for private war
 reserve officers' cadet school