20 C.F.R. § 404.1902
For purposes of this subpart-
Act means the Social Security Act (42 U.S.C. 301 et seq.).
Agency means the agency responsible for the specific administration of a social security system including responsibility for implementing an agreement; the Social Security Administration (SSA) is the agency in the U.S.
Agreement means the agreement negotiated to provide coordination between the social security systems of the countries party to the agreement. The term agreement includes any administrative agreements concluded for purposes of administering the agreement.
Competent authority means the official with overall responsibility for administration of a country's social security system including applicable laws and international social security agreements; the Commissioner of Social Security is the competent authority in the U.S.
Period of coverage means a period of payment of contributions or a period of earnings based on wages for employment or on self-employment income, or any similar period recognized as equivalent under the social security system of the U.S. or under the social security system of the foreign country which is a party to an agreement.
Residence or ordinarily resides, when used in agreements, has the following meaning for the U.S. Residence or ordinarily resides in a country means that a person has established a home in that country intending to remain there permanently or for an indefinite period of time. Generally, a person will be considered to have established a home in a country if that person assumes certain economic burdens, such as the purchase of a dwelling or establishment of a business, and participates in the social and cultural activities of the community. If residence in a country is established, it may continue even though the person is temporarily absent from that country. Generally, an absence of six months or less will be considered temporary. If an absence is for more than six months, residence in the country will generally be considered to continue only if there is sufficient evidence to establish that the person intends to maintain the residence. Sufficient evidence would include the maintenance of a home or apartment in that country, the departure from the country with a reentry permit, or similar acts. The existence of business or family associations sufficient to warrant the person's return would also be considered.
Social security system means a social insurance or pension system which is of general application and which provides for paying periodic benefits, or the actuarial equivalent, because of old-age, death, or disability.
20 C.F.R. §404.1902