Delta Symbol (Δ, δ): Meaning in Maths, Physics and LaTeX
June 3, 2026
The delta symbol is Δ in uppercase and δ in lowercase. Uppercase Δ means “change in” — a finite difference between two values. Lowercase δ means an infinitesimally small change, or one of several specific functions. Copy either below, or jump to how to type it.
| Character | Unicode | HTML entity | LaTeX | Windows alt code |
|---|---|---|---|---|
| Δ uppercase delta | U+0394 | Δ | \Delta | — |
| δ lowercase delta | U+03B4 | δ | \delta | Alt + 235 |
What the symbol means
| Where | Meaning |
|---|---|
| Maths | Change or difference between two values: Δx = x₂ − x₁ |
| Algebra | The discriminant of a quadratic, b² − 4ac |
| Calculus | δ is a vanishingly small change, the step before dx |
| Linear algebra | Kronecker delta δᵢⱼ — 1 when i = j, otherwise 0 |
| Signal processing | Dirac delta δ(x) — an impulse of unit area at zero |
| Chemistry | ΔH, ΔG, ΔS — change in enthalpy, free energy, entropy |
| Finance | Delta — sensitivity of an option price to the underlying |
Δ as change
This is the meaning you meet first. Uppercase delta in front of a quantity means the difference between its final and initial value, and it is always final minus initial — so a falling temperature gives a negative ΔT.
Δ, δ, ∂ and ∇ are four different things
These get mixed up constantly, and using the wrong one changes the meaning of an equation. Δ is a finite, measurable difference. δ is an infinitesimal one. ∂ is a partial derivative, used when a function has more than one variable. ∇ is the gradient operator, which turns a scalar field into a vector.
A common slip is writing ∆ (the increment sign, U+2206) instead of the Greek capital delta U+0394. They look identical in most fonts, but search, spell-check and screen readers treat them differently — prefer the Greek letter.
δ as the Kronecker and Dirac deltas
Two specific functions share the lowercase letter. The Kronecker delta is a discrete switch used all over linear algebra — it is simply the identity matrix written in index notation. The Dirac delta is a distribution: zero everywhere except the origin, with total area one.
Δ as the discriminant
For a quadratic, the sign of the discriminant tells you how many real roots there are before you solve anything: positive gives two, zero gives one repeated root, negative gives none.
How to type it
Windows
- Lowercase δ: hold
Altand type235on the numeric keypad - Uppercase Δ has no legacy alt code. In Word, type
0394and pressAlt + X - Anywhere else, press
Windows + .and search “delta”
Mac
- Uppercase Δ:
Option + J - For δ, open Character Viewer with
Control + Command + Spaceand search “delta”
HTML
ΔorΔfor Δδorδfor δ
In LaTeX
Both cases are single commands and both need math mode. Uppercase Greek is upright by default; \varDelta gives the italic form if you want it to match the lowercase letters.
\Delta is the letter, not an operator, so it takes no automatic spacing. Write \Delta x rather than \Delta \, x — LaTeX already sets it correctly.
Frequently asked questions
What does Δ mean in maths?
Change in, or difference between. Δx is the final value of x minus the initial value, so it can be negative.
What is the difference between Δ and δ?
Δ is a finite, measurable change you could put a number on. δ is an infinitesimal change — the conceptual step towards dx in calculus.
Is δ the same as ∂?
No. ∂ (U+2202, \partial) is specifically the partial derivative symbol, used when a function depends on several variables. δ is a Greek letter.
See also the omega symbol, sigma symbol and theta symbol, or our guide to Greek letters in LaTeX.
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