What does metalloid mean?
A metalloid is a chemical element whose properties fall between those of metals and nonmetals. Many metalloids have a metallic lustre or unusual electrical behavior, but they are generally brittle and may act as semiconductors rather than conducting electricity as metals do. Silicon is the best-known example, while boron and germanium are also commonly included. This intermediate position makes metalloids especially useful in electronics, semiconductor devices, heat-resistant materials, and alloys. The term is mainly technical, appearing in chemistry, physics, geology, and materials science. Although classifications can differ slightly according to the criteria being applied, the underlying concept is clear: a metalloid occupies the chemical boundary between two broad families of elements rather than belonging fully to either one.
A chemical element or substance whose properties are intermediate between those of metals and nonmetals.
"Silicon is a widely used metalloid with important semiconductor properties."
The term is chiefly used in scientific and technical contexts, and the boundaries of the category can vary somewhat between classification systems.
Having the properties of, or characteristic of, a metalloid.
"The compound has a metalloid structure that gives it unusual electrical behavior."
This adjectival use is relatively uncommon and is mostly found in technical writing.
The regular plural is metalloids, with no additional inflection.
"Several metalloids are important in semiconductor manufacturing."
Silicon, the material behind modern electronics, is neither quite a metal nor quite a nonmetal—it is a metalloid, and that middle ground powers the digital world.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does metalloid come from?
Metalloid entered English in the mid-19th century from metal and the combining form -oid, meaning a form or likeness resembling something. Its ultimate elements are Greek metallon, meaning metal, and the suffix -oeidēs, meaning form or likeness. The word reflects the period's effort to name substances that resembled metals in appearance but did not behave fully like them; metallurgy and metallize belong to a related family sharing the same ancient Greek root for metal.
Related word forms
How metalloid is actually used
This is primarily a technical term in chemistry and materials science. The precise membership of the category can vary with the classification criteria used, so lists of metalloids are not always identical across sources. Its use as an adjective is less common than its noun use.
Easily confused with metalloid
A metal is an element with characteristic metallic properties, whereas a metalloid occupies an intermediate chemical and physical position between metals and nonmetals.
A nonmetal is generally classified within a separate elemental category, while a metalloid combines some nonmetal characteristics with a metallic appearance or conductive behavior.