What is "metamerism"

Metamerism \Me*tam"er*ism\, n.

1. (Biol.) The symmetry of a metameric structure; serial symmetry; the state of being made up of metameres.

2. (Chem.) The state or quality of being metameric; isomerism due to different bonding patterns in two substances having the same molecular formula. Contrasted with steroisomerism or optical isomerism. Also, the relation or condition of metameric compounds.

n. 1 (context biology English) The segmentation of the body into similar discrete units 2 (''colorimetry'') The matching of apparent color of objects with different spectral power distributions. 3 (context chemistry English) structural isomerism

In colorimetry, metamerism is a perceived matching of the colors that, based on differences in spectral power distribution, do not actually match. Colors that match this way are called metamers.

A spectral power distribution describes the proportion of total light given off (emitted, transmitted, or reflected) by a color sample at each visible wavelength; it defines the complete information about the light coming from the sample. However, the human eye contains only three color receptors (three types of cone cells), which means that all colors are reduced to three sensory quantities, called the tristimulus values. Metamerism occurs because each type of cone responds to the cumulative energy from a broad range of wavelengths, so that different combinations of light across all wavelengths can produce an equivalent receptor response and the same tristimulus values or color sensation. In color science, such sensations are numerically represented by color matching functions.

Metamerism may refer to:

• Metamerism (biology), in zoology and developmental biology, the property of having repeated segments, as in annelids
• Metamerism (color), in colorimetry, a perceived matching of the colors that, based on differences in spectral power distribution, do not actually match
• The chemical property of having the same proportion of atomic components in different arrangements (obsolete, replaced with isomer)

In biology, metamerism is the phenomenon of having a linear series of body segments fundamentally similar in structure, though not all such structures are entirely alike in any single life form because some of them perform special functions. In animals, metameric segments are referred to as somites or metameres. In plants, they are referred to as metamers or, more concretely, phytomers.