Stratification is the building up of layers. Stratified is an adjective referring to the arranging of layers, and is also the past form of the verb stratify, to separate or become separated into layers. They may refer to:

In mathematics, statistics and applied science

• Stratified sampling
  Stratified sampling
  In statistics, stratified sampling is a method of sampling from a population.In statistical surveys, when subpopulations within an overall population vary, it is advantageous to sample each subpopulation independently. Stratification is the process of dividing members of the population into...
  
  , in statistics
• Stratified fuel charge, or ultra lean burn
  Lean burn
  Lean burn refers to the use of lean mixtures in an internal combustion engine. The air-fuel ratios can be as high as 65:1, so the mixture has considerably less fuel in comparison to the stoichiometric combustion ratio ....
  
  , the use of lean mixtures in an internal combustion engine with unequalized pressure in the cylinder
  • Fuel charge stratification, an internal combustion process using gasoline direct injection
    Gasoline direct injection
    In internal combustion engines, gasoline direct injection , also known as petrol direct injection or direct petrol injection, is a variant of fuel injection employed in modern two-stroke and four-stroke gasoline engines...
    
     to reduce fuel consumption and emissions
    • Fuel stratified injection (FSI), the operation of a stratified fuel charge in an engine using direct injection

In the earth sciences

• Stratification, the layering (strata
  Stratum
  In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...
  
  ) of rocks
  • Stratification (archeology)
    Stratification (archeology)
    Stratification is a paramount and base concept in archaeology, especially in the course of excavation. It is largely based on the Law of Superposition...
    
    , the formation of layers (strata) in which objects are found
  • Stratigraphy
    Stratigraphy
    Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
    
    , the study of geological (or archaeological) stratification and strata
• Atmospheric stratification, the dividing of the Earth's atmosphere into strata
• Stratification (water)
  Stratification (water)
  Water stratification occurs when water masses with different properties - salinity , oxygenation , density , temperature - form layers that act as barriers to water mixing...
  
  , the formation of water layers based on salinity and temperature
  • Lake stratification
    Lake stratification
    Lake stratification is the separation of lakes into three layers:# Epilimnion - top of the lake.# Metalimnion - middle layer that may change depth throughout the day.# Hypolimnion - the bottom layer....
    
    , the dividing of lake water
• Geographic stratification, the dividing of geographic areas

In the social sciences

• Social stratification
  Social stratification
  In sociology the social stratification is a concept of class, involving the "classification of persons into groups based on shared socio-economic conditions ... a relational set of inequalities with economic, social, political and ideological dimensions."...
  
  , the dividing of a society into levels based on power or socioeconomic status

In biology and medicine

• Stratification (botany)
  Stratification (botany)
  In horticulture, stratification is the process of pretreating seeds to simulate natural winter conditions that a seed must endure before germination. Many seed species undergo an embryonic dormancy phase, and generally will not sprout until this dormancy is broken...
  
  , where seeds are pretreated to simulate winter conditions so that germination may occur
• Stratified epithelial lining
  Stratified epithelial lining
  Stratified epithelial lining can refer to:* Stratified squamous epithelium* Stratified columnar epithelium* Stratified cuboidal epithelium...
  
  s, several types of epithelium characterized by multiple layers
• Stratified medicine
  Stratified medicine
  Stratified medicine is the management of a group of patients with shared biological characteristics by using molecular diagnostic testing to select the best therapy in order to achieve the best possible medicinal outcome for that group....
  
  , where patients are grouped according to shared biological traits and diagnostic results
• Population stratification
  Population stratification
  Population stratification is the presence of a systematic difference in allele frequencies between subpopulations in a population possibly due to different ancestry, especially in the context of association studies...
  
  , the stratification of a genetic population based on allele frequencies

See also

• Destratification
  Destratification
  Destratification is a process in which the air or water is mixed in order to eliminate stratified layers of temperature, plant, or animal life. The first example of destratification was in 1919, in a small resorvoir....
  
  
• Strata (disambiguation)
  Strata (disambiguation)
  Strata is the plural of stratum ; for other uses in which it can be used in the singular or plural, see Stratum .Strata may refer to:* Strata , 1990...
  
  
• Stratum (disambiguation)
  Stratum (disambiguation)
  * stratum, the basic unit of lithologic stratigraphy.* stratum or strate, a language influencing or influenced through contact.* Stratum, Netherlands, a city district of Eindhoven....
  
  
• Layer (disambiguation)
• Partition (disambiguation)