Letters should carry meaning,
not decorative noise.

Use lowercase italic letters unless the context gives a stronger convention.

Use t as the independent variable for time-dependent quantities.

State the starting index; do not rely on whether natural numbers include zero.

Define their role locally; keep them lowercase for generic scalars.

Use lowercase names for ordinary functions and always show the input when ambiguity is possible.

Reserve this pair for a linear model when using y=mx+b.

Define them before using du, dv, or integration by parts.

Use lowercase r for an ordinary radius; R is reserved for an outer radius or Taylor remainder.

Capital letters may name sets when membership or set operations make that role explicit.

Capital letters name points; the middle letter in an angle name identifies its vertex.

Area, amount, a named set, or a traditional standard-form coefficient when the page defines that role.

A named set or a traditional standard-form coefficient only when that role is being discussed.

The arbitrary constant of integration, a traditional standard-form coefficient, or a named contextual quantity explicitly defined on the page.

A named antiderivative, implicit relation, cumulative function, or physical force explicitly defined on the page.

A named integral used to collect a cyclic integration equation.

A limit value, linearization, arc length, or explicitly named bound.

A documented maximum derivative bound in an error estimate.

A named proposition in a logic statement.

A named proposition in a logic statement.

A Taylor remainder or the outer radius in the washer method.

Surface area or a sequence of partial sums.

Volume.

Work.