式：equation, formula, expression

How about "formula" instead of "equation"?

 

ChatGPT:

Excellent question.

Both "formula" and "equation" can be correct translations of 式, but they have different nuances, especially in technical or scientific contexts.

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🔍 Difference between "formula" and "equation":

Term	Meaning	Typical Use	Example
Equation	A mathematical statement showing equality (with an equal sign =)	Physics, engineering, mathematics	σ = F / A (stress = force ÷ area)
Formula	A general mathematical expression or rule, often used to calculate something	Chemistry, statistics, product specs	“the formula for calculating area is A = πr²”

Great follow-up — and yes, "expression" is also a possible translation of 式, but its usage differs from "equation" and "formula" in some important ways.

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🔍 Comparison: Expression vs. Equation / Formula

Term	Contains "=" sign?	Typical Use	Nuance
Equation	✅ Yes	Math, science, engineering	A statement of equality (e.g., R = (σ₀ − σ_t)/σ₀)
Formula	✅ Usually	More general; used to calculate something	A known rule for computing a value
Expression	❌ Usually not	Algebraic terms, intermediate steps	A combination of symbols without stating equality (e.g., a + b × c)

 

When "expression" is appropriate:

Use "expression" when referring to a part of a formula or an algebraic phrase that does not stand as a complete equation, e.g.:

• “The right-hand expression in Equation (1)…”

• “This expression is substituted into…”