Initial, original, primordial can all mean existing at or constituting the beginning or start of a thing, especially of a thing that gradually assumes shape or form or that manifests itself in many ways.
Nevertheless, in spite of this agreement in meaning, the words are rarely interchangeable, usually because of additional and differing implications, but often also because of the determination of their use by idiom.
Initial, in general, is used in reference to things seen as a whole, often in fact but sometimes in thought; the term, therefore, usually implies an end or completion.
Original (see also NEW ) is used especially with reference to what is the very first in order or constitutes the ultimate beginning or source; in this sense it usually connotes the idea of being underived or unimitated and implies that there is nothing from which the original thing has sprung.
A court that has original jurisdiction has the right to try a cause to determine both the facts and the application of the law to them, as distinguished from a court with appellate jurisdiction. "Original sin " was committed by Adam and Eve as the first human beings but, in theological use, the phrase also means that sin as it leaves its traces upon every human being.
Sometimes, however, original means something more specific; thus, the original owner of a piece of land would strictly be the one who first held it by a natural or legal right, but in legal interpretation the phrase may be used of an earlier owner when successive owners are mentioned; an author's original work may be the work first produced by him, but more often it means (without regard to order of writing) a work independently conceived and executed by him.
Primordial (see also PRIMARY ) is comparable with initial and original through its implied reference to what forms the actual beginning or starting point or the earliest form taken by something that follows a course, an evolution, a progression, or an unfolding.