According to the Ohio website:
A Resident of Ohio is an individual that lived in Ohio for the entire year.
A Nonresident of Ohio is an individual that was domiciled outside of Ohio for the entire tax year. You spent no more than 212 contact periods in Ohio during the tax year.
A Part-Year Resident of Ohio is an individual that moved into or out of Ohio during the tax year.
If one spouse is a resident and the other is not, file a joint return and indicate each spouse's residency. You must file the same as you did on the federal return.
For more information: