How is a citizen or resident of the Virginia Commonwealth defined? 

Under the Virginia Constitution, a prospective voter must be a resident of the precinct where he seeks to register. In order to establish "residency", a prospective voter must show that (1) he has an actual physical place of abode in the precinct, and (2) he is domiciled there.  

And, according to the Virginia Tax Department, individuals who are physically present in Virginia, or who maintain a place of abode here for more than 183 days during the taxable year are actual residents. The period of residency does not have to be consecutive days. Most Virginia residents are actual residents of Virginia.

It is possible to be an actual resident of Virginia and a domiciliary resident of another state. For example, dual status commonly occurs when a resident of another state enrolls in a Virginia school and lives here during the school year.

Individuals whose state of legal residence in the technical sense is Virginia are domiciliary residents. Most domiciliary residents actually live in Virginia.

An individual who enters the military from Virginia (i.e., claims Virginia as his/her home of record) will remain a domiciliary resident of Virginia, unless appropriate steps are taken to abandon Virginia as the state of domicile.

A student who attends school in another state, but maintains Virginia as his/her legal state of residence, is a domiciliary resident. 

And a resident of Virginia who accepts employment in another country is a domiciliary resident, unless appropriate steps are taken to abandon Virginia as the state of domicile.