Heterogeneous is an adjective used to describe an object or system consisting of multiple items having a large number of structural variations. It is the opposite of homogeneous, which means that an object or system consists of multiple identical items. Matters of a quantum can exist in homogenous or in heterogeneous or in combined distributions. The term is often used in a scientific (such as a kind of catalyst), mathematical, sociological or statistical context.

Physics and chemistry

A heterogeneous mixture is a mixture of two or more compounds. Examples are: mixtures of sand and water or sand and iron filings, a conglomerate rock, water and oil, a salad, trail mix, and concrete (not cement). During the sampling of heterogeneous mixtures of particles, the variance of the sampling error is generally non-zero. Gy's sampling theory quantitatively defines the heterogeneity of a particle as:

$h\_i\; =\; \backslash frac\{(c\_i\; -\; c\_\backslash text\{batch\})m\_i\}\{c\_\backslash text\{batch\}\; m\_\backslash text\{aver\}\}\; .$

where $h\_i$, $c\_i$, $c\_\backslash text\{batch\}$, $m\_i$, and $m\_\backslash text\{aver\}$ are respectively: the heterogeneity of the $i$th particle of the population, the mass concentration of the property of interest in the $i$th particle of the population, the mass concentration of the property of interest in the population, the mass of the $i$th particle in the population, and the average mass of a particle in the population.

In chemical kinetics, a heterogeneous reaction is one that takes place at the interface of two or more phases, i.e. between a solid and a gas, a liquid and a gas, or a solid and a liquid. In heterogeneous catalysis the catalyst is in a different phase from the substrate.

Statistics and econometrics

See Study heterogeneity.

Systems

In the world of enterprise computing, heterogeneous data is a mix of data from two or more sources, often of two or more formats, e.g., SQL and XML.

Distributed systems are called heterogeneous if they contain many different types of hardware and software.

Taxonomy

In taxonomy, a heterogeneous taxon is a taxon that contains a great variety of individuals or sub-taxa; usually this implies that the taxon is an artificial grouping.

Genetics

In genetics, heterogeneity refers to multiple origins causing the same disorder in different individuals. If a number of different mutations occurring the same gene produce disorders, it is said to manifest allelic heterogeneity. This term has been used when a number of different alleles cause a similar phenotype or different phenotypes.

Example diseases:

• Different FBN1 mutations causing Marfan's syndrome
• Cystic fibrosis is caused by greater than 900 different mutant alleles
• Alpha-Thalassemia or sickle cell anemia can be caused by different mutations in alpha-globin gene.