---
term: "Young's Modulus"
category: "material-testing"
shortDefinition: "The proportionality constant E between uniaxial stress and elastic strain in Hooke's regime (σ = Eε); slope of the initial linear region on a stress–strain curve for isotropic materials."
formula: "E = σ / ε  (elastic, small strain)"
relatedStandards: ["ISO 6892-1"]
url: "https://vectorbtc.com.tr/resources/glossary/youngs-modulus/"
---

**Young’s modulus (E)** characterizes **stiffness** in the elastic regime: how much stress is required to produce a small recoverable strain. For isotropic homogeneous solids under uniaxial tension or compression, **σ = Eε** holds until proportional limit or yield supersedes linearity.

E is determined from the **slope of the stress–strain curve** in the initial linear region. High-precision measurement requires **high-resolution extensometers** or non-contact strain measurement and subtraction of **machine and grip compliance**, which otherwise underestimate E.

For polycrystalline metals, E is relatively insensitive to microstructure compared to yield strength, but **texture** in rolled sheet can produce apparent directional moduli if off-axis specimens are tested. Composites and polymers exhibit viscoelasticity; “modulus” then depends on **time, temperature, and strain rate**.

Designers use E with second moments of area to estimate **deflections, resonant frequencies, and buckling loads**. It should not be confused with **tangent modulus** or **secant modulus** used beyond yield in nonlinear analysis.