Limit of a real function
A finite limit controls output error through sufficiently small input distance.
Key knowledge
The limit of f(x) as x approaches a is L if every positive output tolerance ε admits a positive input tolerance δ such that 0 < |x−a| < δ implies |f(x)−L| < ε.
Values and equations
limₓ→ₐ f(x) = L
- f
- Real-valued function
- a
- Approached input
- L
- Finite limiting output
Conditions and scope
- Here f is real-valued and defined on a punctured open interval around a.
- The value f(a) may differ from L or be undefined; infinite and one-sided limits have separate definitions.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Finite two-sided epsilon-delta definition.
2026-10-10 · Checked quantifier order, punctured neighbourhood and finite-real scope.
Foundational review
2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.
Sources from other places
Agreement within this scope
Punctured epsilon–delta real finite limits.
The source allows general accumulation-point domains; the repository punctured interval is a valid narrower case.
Universidade de São Paulo, Instituto de Matemática e Estatística
- Cálculo I · Agenda 05: Limites BrazilPortuguese
§1, Definição 1, p.3
- Cálculo I · Agenda 05: Limites
Entry details
Permanent link to this entry ↗- Record identity
- math-limits
- Revision
- core.1
- Structured reference record
- Essential core · first collection