- Harmony. A quality that represents and appropriate and congruent arrangement of parts, as in an arrangement of varied architectural and landscape elements.
- Hazardous materials. Materials or wastes that either cause or contribute to an increase in mortality, serious illness, or otherwise pose a substantial treat to human or environmental health when improperly managed.
- Hazardous waste facilities. Carefully designed off-site facilities accepting hazardous wastes for storage or treatment.
- Heliport. An identifiable area on land or water, including any building or facilities thereon, used or intended to be used for the landing and takeoff of helicopters. Does not include temporary landing and takeoff sites. Refueling and overnight maintenance are permitted.
- Helistop. An identifiable area on land or water, including any building or facilities thereon, used or intended to be used for the landing and takeoff of helicopters. Does not include temporary landing and takeoff sites. Refueling and overnight maintenance are not permitted.
- Historic resources. Buildings, structures, sites, or districts that are considered of particular historical and/or cultural significance. Generally, such resources are listed on a local, state, or federal register.
- Historic treatment. The memorialization, preservation, reconstruction, rehabilitation, or restoration of a historic resource.
- Historic memorialization. Permanent recognition of an important historical resource through such means as a physical plaque or official designation.
Historic preservation. A treatment for a historic building or landscape that focuses on the maintenance and repair of existing historic materials and retention of a property’s form as it has evolved over time. - Historic reconstruction. A treatment for a historic building or landscape that re-creates vanished or non-surviving portions of a property for interpretive purposes.
- Historic rehabilitation. A treatment for a historic building or landscape that acknowledges the need to alter or add to a historic property to meet continuing or changing uses while retaining the property’s historic character.
- Historic restoration. A treatment for a historic building or landscape that depicts a property at a particular period of time in its history, while removing evidence of other periods.
- Holistic approach. An approach that addresses the factors that lead to a condition or behavior as well as the treatment of symptoms or enforcement of laws, in order to prevent a condition or behavior.
- Household. The U.S. census considers all persons living in a dwelling unit to be a household, whether or not they are related. Both a single person living in an apartment and a family living in a house are considered households.