After the development of Inflection, however, that one of several kindred words which seemed the simplest was regarded as the primitive form, and from this the other words of the group were thought to be derived. Such supposed processes of formation were then imitated, often erroneously, and in this way new modes of derivation arose. Thus new adjectives were formed from nouns, new nouns from adjectives, new adjectives from verbs, and new verbs from adjectives and nouns.
In course of time the real or apparent relations of many words became confused, so that nouns and adjectives once supposed to come from nouns were often assigned to verbs, and others once supposed to come from verbs were assigned to nouns.
Further, since the language was constantly changing, many words went out of use, and do not occur in the literature as we have it. Thus many Derivatives survive of which the Primitive is lost.
Finally, since all conscious word-formation is imitative, intermediate steps in derivation were sometimes omitted, and occasionally apparent Derivatives occur for which no proper Primitive ever existed.