Glossary H

Hand control is described as a mechanical system that allows for operation of both the gas and brake pedals by either hand and is accomplished by means of a combination lever mounted to the steering column.

Hairspring is defined ad a fine spiral spring that regulates the movement of the balance wheel in a timepiece. Also known as balance spring, this is the small spiral spring that is attached to the balance wheel, the quality of which can affect the regularity and accuracy of a movement.

Horizontal classification means a grouping of species from a similar time interval of evolution rather than those sharing a common lineage (horizontal with respect to a phylogenetic tree). Compare --->'vertical classification'.

A Handheld vacuum is a machine which is portable and sometimes cordless which make them ideal for cleaning small areas like the car. In addition to upright vacuums, it is good to use handheld vacuums because they can clean areas which an upright can not clean because they are too large.

Hair-curlers and curling irons are heating devices designed to curl human hair. Both hair curlers and curling irons contain heating elements controlled by a thermostat. In addition, a thermal cutoff or fuse prevents appliance burnouts due to overheating.

The term hydrate may refer to the following:

• to cause a person or object to absorb water or other liquid
• a chemical substance containing water or its constituent elements

The term harvest may refer to the following:

• the process of gathering mature crops from fields
• IBM 7950 Harvest, a one-of-a-kind adjunct to the NSA's IBM 7030 Stretch supercomputer
• Harvest project, a web cache research project
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The term handheld refers to any object that is designed to be light and small enough to be held and/or operated with one or both hands.