The Guild of One-Name Studies defines a variant as a name spelling which varies from the primary name spelling (or another variant spelling) used by that person's ancestors and which is:

• A name spelling that the person was known to have used, through signature evidence on wills, marriage bonds etc or other documents originating from the individual concerned, or
• A name spelling used by officials on a consistent and persistent basis over a period of years.

The starting point of any discussion of variants and deviants must be that in former times, not only did names get recorded with a wide range of spellings, but individuals themselves may have used many versions too - it is said that Shakespeare spelt his own name in six or more different ways over his lifetime, from evidence of known signatures. Additionally, many people were illiterate and could not sign their own name, so it is not possible to say that any given spelling was 'used' by the individual. Officialdom will have recorded their name and this may have become the adopted and accepted spelling of the name; indeed, this is the likely method by which variants arose. It can often be seen that the recorded spelling in parish registers changes with the change of incumbent. Should all such spellings be considered as variants? The Guild of One-Name Studies'ss advice is that it depends on the consistency with which the name is recorded in official documents. If the vicar consistently used a given spelling over many years, then it may be considered as a variant, bearing in mind that such records might have been called on as evidence in things like settlement disputes or probate. On the other hand, vicars, like anyone else, might use a large range of spelling variants with no particular pattern and these should in general be considered deviants. 

A deviant is any other spelling recorded, including cases where the spelling occurs in official records, but only randomly and inconsistently. Deviants will also include spellings derived from enumeration, transcription and indexing errors, both contemporary and modern.