Glossary H

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.

Harpsichord (in Italian cembalo; and in French clavecin) is defined as a stringed keyboard instrument in which the strings are plucked to produce sound.

Anchor (or hook) is described as a metal device that is lowered from the boat on rope or chain (anchor rode) and that digs into or lies on the water's bottom and so holds the boat. To set the anchor is to help it dig in by pulling hard on the rode.