Where does pyramid collide?

A solid figure with a polygon for its base and triangular faces that meet at a single apex above the base: Euclid's Elements (around 300 BCE) treated the pyramid in Book XII and proved that its volume is one third of a prism standing on the same base with the same height. The figure is fixed entirely by its faces, edges, and vertices, with no reference to material or scale. This referent is an idealised shape in geometry, not the stone monument that gave it its name, the feeding diagram of an ecosystem, or a layer of a market.[1]

Unit

One pyramid solid, fixed by its base polygon, apex, and height

Recovery means

Not applicable

Measured by

Described by base area and height, with volume equal to one third of base area times height

A diagram of a food chain in which each feeding level is drawn as a horizontal bar, stacked from many organisms or much energy at the base to few at the top: Charles Elton's 1927 Animal Ecology introduced the pyramid of numbers, the observation that animals grow scarcer at each step up the chain. Raymond Lindeman's 1942 paper The trophic-dynamic aspect of ecology recast the picture in terms of energy, showing how much less energy reaches each higher feeding level. The referent is a quantitative summary of who eats whom in an ecosystem, unrelated to a stone monument, a geometric solid, or a market.[2][3]

Unit

One feeding level's count, biomass, or energy, stacked into a pyramid

Recovery means

Not applicable

Measured by

Quantified by counts of organisms, standing biomass, or energy flow at each feeding level

The very large population of the world's poorest people, viewed as an untapped consumer market rather than only as aid recipients: C. K. Prahalad and Stuart Hart's 2002 article The fortune at the bottom of the pyramid argued that firms could serve billions of low-income customers profitably while raising their living standards. Ted London and Stuart Hart's 2004 paper Reinventing strategies for emerging markets refined the idea toward business models built with, not just for, poor communities. The referent is a layer of a global income distribution treated as a market, and it has nothing in common with a royal tomb, a geometric solid, or a food chain.[4][5]

Unit

The lowest income tier of the global market, by population and purchasing power

Recovery means

Not applicable

Measured by

Sized by the number of people below an income threshold and their aggregate purchasing power