Русско-англо-русский юридический словарь

Among the typcal conditions that must be met before an employee can exercise the option that has been granted to him, it is frequently required that the employee continues to work for the employer during a certain period of time. To the extent that such a condition must be met before the option becomes exercisable, that condition has, in many countries, the legal nature of a condition precedent (common law) or suspensive condition (civil law). The option is not considered to have vestee before such a condition has been met. (Model Tax Convention on Income and on Capital 2010 By OECD)

A condition precedent is one which must be performed before the estate will vest, or before the obligation is to be performed. (lectlaw.com)

A contract or contractual obligation can be made to depend upon the occurrence of a future uncertain event, so that it takes effect only if the event occurs. Under the Principles this is a suspensive condition. In some jurisdictions it is known as "condition precedent". (UNIDROIT PRINCIPLES 2010)

A contract is made subject to a condition precedent and the condition is satisfied on or before that date. (revenue.ie)