An Arizona only dependent is generally an individual over the age of 65 that doesn’t qualify as a Federal dependent, but does qualify as a dependent under special Arizona rules.
See the following from page 7 of AZ 2016 Form 104 instructions:
A person who is age 65 or over (related to you or not) that does not qualify as your dependent on your federal return, but one of the following applies:
In 2016, you paid more than one-fourth of the cost of keeping this person in an Arizona nursing care institution, an Arizona residential care institution, or an Arizona assisted living facility. Your cost must be more than $800.
- In 2016, you paid more than $800 for either Arizona home health care or other medical costs for the person.