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Showing 1681–1709 of 1709 reference entries

Measurement · PhysicsRadiant flux, intensity, irradiance, exitance and radiance

Optical power, directional power and surface densities are different quantities.

DefinitionMeasurement · PhysicsPhotometric weighting, lumen, candela, lux and luminance

Photometry weights radiation with a specified standard visual response.

DefinitionMeasurementWriting SI quantities and unit symbols

Symbol form, spacing and parentheses preserve the meaning of reported quantities.

DefinitionMeasurementGram prefixes and the kilogram exception

Mass prefixes attach to gram even though kilogram is the SI base unit.

DefinitionMeasurementRounding a result with its uncertainty

Report useful digits without treating extra digits as proof of accuracy.

MethodMeasurement · Physics · ChemistryCommon non-SI units and exact SI conversions

Common non-SI unit names require their correct SI scale factors.

DefinitionPhysics · ChemistryGas pressure as molecular momentum transfer

Molecular collisions link macroscopic pressure to random translational motion.

ModelChemistry · PhysicsOrdinary aggregate states and bulk behavior

Solid, liquid and gas describe bulk behavior rather than chemical identity.

ModelChemistryInferring empirical and molecular formulas from composition

Element mass ratios become atom ratios through molar masses, with uncertainty and sample identity retained.

MethodChemistryLewis structures and valence-electron accounting

A Lewis diagram accounts for bonding and nonbonding valence electrons in a specified connectivity.

MethodChemistryElectron-domain geometry and molecular shape

VSEPR distinguishes the arrangement of electron regions from the positions of atoms.

ModelChemistryElectronegativity, bond polarity and molecular polarity

Polar bonds can cancel in a molecule; molecular geometry matters.

ModelChemistrySolutions, solutes, solvents and solvation

Dissolution disperses specified molecular or ionic species in a solvent.

DefinitionChemistrySolubility, saturation and supersaturation

A saturation limit is an equilibrium property under specified conditions, not a synonym for concentration.

DefinitionChemistryFiltration separates retained solids from a fluid

Ordinary filtration separates undissolved particles; dissolved species can remain in the filtrate.

MethodChemistryDistillation and vapor–liquid composition

Distillation uses vapor–liquid partitioning and condensation, with a limit at an azeotrope.

MethodBiologyGene, allele, genotype and phenotype

Genomic sequence variants and observable traits describe different levels of biological information.

DefinitionBiology · ChemistryEnzyme substrates, active sites and induced fit

Substrate recognition and catalysis depend on a dynamic molecular environment.

ModelBiology · ChemistryMonomers, polymers and hydrolysis

Covalent subunit linkage and water-assisted cleavage explain biological polymer structure.

DefinitionBiology · ChemistrySugars, glycosidic linkages and polysaccharides

Sugar connectivity distinguishes energy-storage and structural polysaccharides.

DefinitionBiology · ChemistryFatty acids, storage lipids and membrane lipids

Lipids include several architectures rather than one repeating-monomer polymer class.

DefinitionBiology · ChemistryAmino-acid residues and peptide linkages

The peptide backbone and variable side chains are different parts of protein structure.

DefinitionBiology · ChemistryNucleotides and DNA/RNA backbone polarity

Bases carry sequence information on a chemically directional sugar–phosphate backbone.

DefinitionBiologyCell membrane, cell wall, cytosol and compartments

A cell's boundary, fluid interior and specialized structures have different roles.

DefinitionEarth & cosmos · MeasurementEarthquake location, source magnitude and local intensity

A source location or magnitude does not describe the shaking experienced at every site.

DefinitionEarth & cosmosAtmospheric composition and thermal layers

Composition and temperature structure describe different features of Earth's atmosphere.

ModelEarth & cosmosDrainage basins, outlets and water divides

Surface drainage boundaries depend on the chosen outlet and need not bound groundwater flow.

DefinitionEarth & cosmosThe celestial sphere and the observer's sky

A sky direction is an angular observation, not an object's three-dimensional distance.

ModelEarth & cosmos · MeasurementRight ascension, declination and reference epochs

Celestial angular coordinates require a declared reference system and date conventions.

Definition
DefinitionSource checked

Gram prefixes and the kilogram exception

Measurement

Mass prefixes attach to gram even though kilogram is the SI base unit.

Key knowledge

The kilogram is the SI base unit of mass and already contains the historical prefix kilo. Decimal multiples and submultiples of mass are named by attaching one prefix to gram, not by stacking a new prefix on kilogram: 1 mg=10⁻⁶ kg and 1 μg=10⁻⁹ kg.

Values and equations

1 g=10⁻³ kg; 1 mg=10⁻³ g=10⁻⁶ kg; 1 μg=10⁻⁶ g=10⁻⁹ kg

g,kg,mg,μg
Gram, kilogram, milligram and microgram unit symbols mass units

Conditions and scope

  • Use prescribed symbol case: mg is milligram and Mg is megagram.
  • The gram is 10⁻³ kg; this convention does not make gram the SI base unit.
Sources · 3

References

Sources retain their recorded scope. A source link alone does not establish verification of every statement.

  1. The International System of Units, 9th edition, version 4.01 (2026)Bureau International des Poids et Mesures (BIPM)Reference guidebipm.orgRead source
  2. Metric (SI) PrefixesNational Institute of Standards and TechnologyReference guidenist.govRead source
  3. O Sistema Internacional de Unidades (SI) · 2ª edição luso-brasileiraInmetro and Instituto Português da QualidadeReference guide · PDFgov.brRead source

Evidence and review

Prefixed mass units are formed from gram; exact decimal factors relate kilogram, gram and microgram.

2026-10-10 · Independent Chemistry, Biology and Earth/Cosmos editor (AI editorial review). Source checks and independent AI editorial review of compact reference claims, equations, units, conditions and conceptual mappings. This is not human specialist certification, laboratory accreditation, whole-book verification, or a claim that all possible foundational knowledge is present.

Foundational review

2026-10-10 · Independent AI editorial inspection of this new compact reference entry, its equations, applicability, sources and knowledge connections.

Sources from other places

Agreement within this scope

Mass multiples use prefixes attached to gram, despite kilogram being the base unit.

Case-sensitive prefixes distinguish mg, µg and Mg.

Related reference entries

Explore relationships within this area of study and its connections to other areas.

Showing 1–2 of 2 relationships

Scientific relationships · 2 / 2

The relationship type describes the connection. Its linked statements, sources and conditions define the scope.

  1. Uses definition
    Relationship sources · 2

    Linked statements

    • The kilogram is the SI base unit of mass and already contains the historical prefix kilo. Decimal multiples and submultiples of mass are named by attaching one prefix to gram, not by stacking a new prefix on kilogram: 1 mg=10⁻⁶ kg and 1 μg=10⁻⁹ kg.

    Uses kilogram as the base mass unit.

  2. Uses definition
    Relationship sources · 2

    Linked statements

    • The kilogram is the SI base unit of mass and already contains the historical prefix kilo. Decimal multiples and submultiples of mass are named by attaching one prefix to gram, not by stacking a new prefix on kilogram: 1 mg=10⁻⁶ kg and 1 μg=10⁻⁹ kg.

    Uses the exact decimal factors milli and micro while explaining the special attachment convention.

Entry detailsPermanent link to this entry ↗
Record identity
foundation-measurement-mass-prefixes
Revision
foundations-audit.1
Structured reference record
Foundational core completion