53 Pa. C.S. § 8572
The following words and phrases when used in this subchapter shall have the meanings given to them in this section unless the context clearly indicates otherwise:
"Base payment." The amount of property tax paid by an applicant in the base year.
"Base year." The tax year preceding the first tax year for which a taxing authority implements the provisions of this subchapter or the tax year immediately preceding an applicant's entry into the tax deferral program.
"Claimant." A person whose household income does not exceed the limit provided for in section 8574 (relating to income eligibility).
"Household income." All income as defined in the act of March 11, 1971 (P.L. 104, No. 3), known as the Senior Citizens Rebate and Assistance Act, received by the claimant and by the claimant's spouse during the calendar year for which a tax deferral is claimed.
"Increase in real property taxes." An increase in the property taxes above the base payment resulting from a millage increase a change in the assessment ratio or method, or by a revaluing of all properties.
53 Pa.C.S. § 8572