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physics2u.com/symbols.html
Notation contract · one meaning per symbol, sitewide

Symbols & Glossary

Every glyph below carries exactly one meaning across the whole site. Where a symbol is first defined rigorously, its row cites the derivation that introduces it — follow the cite to see the object built from scratch, not merely named.

S
Action
Functional of a path; SI units J·s. The quantity a physical trajectory renders stationary.
intro d-001
L
Lagrangian
Equal to T−V for a large class of systems; SI units J. Integrand of the action.
intro d-001
Hamiltonian
Legendre transform of L in the velocities; generates time evolution. Equals total energy when L has no explicit time dependence.
intro d-004
β
Inverse temperature
Defined as 1/kT with k the Boltzmann constant; SI units J−1. Natural variable of the canonical ensemble.
intro d-013
ψ
Wavefunction
Probability amplitude; |ψ|2 is a probability density. Complex-valued state of a quantum system.
intro d-007
reference

Glossary

Plain-language definitions of recurring terms — functional, stationary path, degree of freedom, ensemble, observable. Each entry states the term in one sentence, then links to the first derivation where it does real work.

Tier 2 entries add the operational definition (how the quantity is measured or computed).

reference

Constants

Fundamental constants used sitewide with fixed symbols: c speed of light reduced Planck k Boltzmann G gravitation.

Values are quoted to the precision each derivation needs; a units check accompanies every appearance so dimensions are always auditable.