The word "church" has an interesting ancestry.  It most likely began as a Germanic word that entered the Greek language and then moved on to English.  The Greek word, κυριακός, means for or of an owner, master or lord (κύριος means master or lord, as in kyrie eleison, Lord have mercy). 

Whatever the word's etymological roots, it is another matter entirely to define what a church is.  The California Financing Law does not attempt to define "church" but it does specify how to determine what constitutes a "church":

What constitutes a “church” shall be determined from the following criteria, none of which has controlling weight: a distinct legal existence; a recognized creed and form of worship; a definite and distinct ecclesiastical government; a formal code of doctrine and discipline; a distinct religious history; a membership not associated with any other religion or denomination; a complete organization of ordained ministers ministering to their congregations; ordained ministers selected after completing prescribed courses of study; a literature of its own; established places of worship; regular congregations; regular religious services; schools for the religious instruction of youth; and schools for the preparation of its ministers.

Cal. Fin. Code § 22061(b)(2).   Readers may recognize these factors as being substantially similar to the factors listed in the Internal Revenue Service's Tax Guide for Churches and Religious Organizations.

Some readers may question why the CFL concerns itself with churches at all.  The reason is that the CFL exempts "nonprofit church extension funds" which are defined as "a nonprofit organization affiliated with a church, that is formed for the purpose of making loans to that church’s congregational organization or organizations for site acquisitions, new facilities, or improvements to existing facilities, purchased for the benefit of the church congregational organization".  Cal. Fin. Code § 22061(b)(1).

Although the word "church" is commonly used in reference to the Christian religion, the CFL factors listed above do not on their face exclude other religious traditions.