Subscript in LaTeX: _, Braces, Superscripts, and Common Errors

To write a subscript in LaTeX, use _ in math mode: x_1. Use ^ for a superscript: x^2. Braces are required when more than one character belongs in the lower or upper position, as in x_{12} or x^{2n}.

Copy-paste syntax: $x_1$ , $x_{n+1}$ , $x^2$ , and $x^{2n}$ . Put the expression in math mode and group multi-character subscripts or superscripts with {...}.Prerequisites: Basic LaTeX knowledge. For math mode basics, see Mathematical Expressions.Last updated: April 2026 | Reading time: 12 min | Difficulty: Beginner to Intermediate

What You’ll Learn

✅ Basic LaTeX subscript and superscript syntax for mathematical notation
✅ Multiple character subscripts and compound superscript expressions
✅ Special cases (limits, operators, tensor notation)
✅ Chemical formula subscript notation and isotopes
✅ Advanced subscript positioning and formatting techniques
✅ Common subscript errors and how to fix them
✅ Best practices for readable mathematical notation

Frequently Asked Questions

What is the difference between subscripts and superscripts in LaTeX?

In LaTeX, subscripts are notations placed below the baseline using the underscore character (_), commonly used for indices and chemical formulas. Superscripts are placed above the baseline using the caret character (^), typically for exponents and powers. Both are essential for mathematical and scientific notation in professional documents.Quick Example:

Subscript: x_1 renders as x₁
Superscript: x^2 renders as x²

How do I write multiple character subscripts in LaTeX?

Always use braces {} to group multiple characters in a LaTeX subscript or superscript. Without braces, only the first character becomes a subscript.Correct subscript syntax:Wrong syntax:This is one of the most common subscript errors in LaTeX.

Why do I get a 'Double subscript' error in LaTeX?

The “Double subscript” error occurs when you try to apply two subscripts to the same variable without proper grouping:Solutions:

Use nested braces if one subscript depends on another:

Or separate them with an empty group:

How do I use subscripts in chemical formulas?

For chemical formula subscript notation, enclose the formula in \mathrm{} and use subscripts for atom counts:For better chemistry support, use the mhchem package:

What's the correct syntax for tensor notation subscripts?

Tensor notation typically places superscripts before subscripts for contravariant and covariant indices:The tensor package can simplify pre-superscripts and pre-subscripts in tensor notation.

Can I use subscripts in LaTeX text mode (outside of equations)?

Yes! Use \textsubscript{} and \textsuperscript{} commands for text mode subscript notation:Alternatively, use math mode notation within text:

How do I avoid deeply nested subscript errors?

Avoid excessive subscript nesting beyond 2-3 levels, as it becomes hard to read:Acceptable nesting:Problematic nesting:Best practice: For complex notation, break expressions into parts for clarity.

What's the best practice for mathematical indices in research papers?

Consistency guidelines for academic subscript notation:

Index naming: Use consistent single letters (i, j, k) throughout
Coordinate systems: Stick to one notation style consistently
Vector notation: Use either subscripts or superscripts consistently
Summation indices: Follow Einstein summation convention in physics
Semantic meaning: Choose meaningful indices: v_x instead of v_1 for x-component

Basic Syntax

Subscripts (Indices)

Expected output

Single character:

x_1

x_2

x_n

Multiple characters:

x_{12}

x_{n+1}

x_{max}

Variables:

a_i

b_j

c_{ij}

Greek letters:

\alpha_1

\beta_{n}

\gamma_{i,j}

Superscripts (Exponents)

Expected output

Single character:

x^2

x^n

x^*

Multiple characters:

x^{10}

x^{2n}

x^{n+1}

Common exponents:

e^x

2^n

10^{-3}

Special notations:

x^{\prime}

x^{\dagger}

x^{\ast}

Important Rule: Braces for Multiple Characters

Critical: Without braces, only the first character after _ or ^ becomes sub/superscript:

x_12 renders as x₁2 (only 1 is subscript)
x_{12} renders as x₁₂ (both 1 and 2 are subscript)

Combined Subscripts and Superscripts

Basic Combinations

Expected output

Both subscript and superscript:

x_1^2

a_n^m

x_i^{j+1}

Order doesn’t matter:

x_1^2 = x^2_1

Complex combinations:

x_{n+1}^{2m}

a_{ij}^{kl}

With operators:

\displaystyle\sum_{i=1}^n

\displaystyle\int_0^{\infty}

Tensor notation:

T_{\mu\nu}^{\rho\sigma}

Nested Subscripts and Superscripts

The preview demonstrates every nesting pattern from the source in one compiled page. Prefer the shallowest notation that communicates the structure, and add braces explicitly at each level so the grouping remains readable and maintainable.

Special Use Cases

Limits and Operators

The compiled result above shows the important layout difference: inline limits keep their condition beside the operator, while display-style limits, sums, products, integrals, and multi-line conditions place their scripts in the conventional display positions. Use the source and preview together to compare the exact input with the typeset result.

Chemical Formulas

Expected output

Basic chemical formulas:

\mathrm{H_2O}

\mathrm{CO_2}

\mathrm{H_2SO_4}

Isotopes:

^{14}\mathrm{C}

^{235}\mathrm{U}

^{2}\mathrm{H}

Ions:

\mathrm{Na^+}

\mathrm{Cl^-}

\mathrm{SO_4^{2-}}

Chemical equation:

2\mathrm{H_2} + \mathrm{O_2} \rightarrow 2\mathrm{H_2O}

Physics and Engineering Notation

Expected output

Vector components:

\vec{v} = v_x\hat{i} + v_y\hat{j} + v_z\hat{k}

Derivatives:

\frac{d^2y}{dx^2}

\frac{\partial^2 f}{\partial x^2}

Tensors:

g_{\mu\nu}

R^{\alpha}_{\beta\gamma\delta}

Four-vectors:

x^\mu = (ct, x, y, z)

Christoffel symbols:

\Gamma^{\lambda}_{\mu\nu}

Units:

10^{-9}\,\mathrm{m}

3.0 \times 10^8\,\mathrm{m/s}

Advanced Techniques

Primes and Multiple Primes

Expected output

Single prime:

f'(x)

y'

Multiple primes:

f''(x)

f'''(x)

Alternative notation:

f^{\prime}(x)

f^{\prime\prime}(x)

With subscripts:

x'_1

x''_n

Prime on subscript:

x_{n'}

x_{n''}

Positioning and Spacing

Accents with Sub/Superscripts

Expected output

Accents with subscripts:

\hat{x}_i

\tilde{y}_n

\bar{z}_k

Accents with superscripts:

\hat{x}^2

\vec{v}^T

\dot{x}^n

Combined:

\hat{x}_i^2

\tilde{\phi}_{nm}^{kl}

Wide accents:

\widehat{xyz}_1^2

\widetilde{ABC}_{ij}

Text Mode Subscripts and Superscripts

Expected output

In text mode: H

_2

O is water. E = mc

^2

is Einstein’s equation.Ordinals: 1

^{\text{st}}

, 2

^{\text{nd}}

, 3

^{\text{rd}}

Footnote markers: Text

^{\text{a}}

, Reference

^1

Common Errors and Solutions

Error: Double subscript

Problem: x_a_b causes “Double subscript” error.Solution: Use braces to clarify structure:

Only first character is sub/superscript

Problem: x_12 shows as x₁2 instead of x₁₂.Solution: Always use braces for multiple characters:

Subscripts in limit are inline

Problem: Limits appear cramped in inline math.Solution: Use display style or \limits:

Prime notation conflicts

Problem: x'^2 doesn’t work as expected.Solution: Use proper grouping:

Best Practices

1. Readability Guidelines

Good Practices:

Use meaningful subscripts: v_x not v_1 for x-component
Avoid deep nesting: x_{i_j} is okay, deeper is confusing
Be consistent: If using i,j,k for indices, stick to it
Use semantic notation: \max not max

Poor Practices to Avoid:

Overusing sub/superscripts: x_{a_{b_{c_{d}}}}
Mixing notation styles in same document
Using subscripts for non-mathematical text
Forgetting braces: x_min instead of x_{min}

2. Consistency Rules

Indices: Use consistent letters (i, j, k or m, n, p)
Coordinates: Be consistent (x, y, z or r, θ, φ)
Time derivatives: Choose notation and stick to it (ẋ or dx/dt)
Vector components: Consistent notation (subscripts or superscripts)

3. Special Notation Standards

4. Accessibility Considerations

Avoid excessive nesting that’s hard to read
Use \text{} for words in subscripts: x_{\text{max}}
Consider alternative notations for complex expressions
Break very complex expressions into parts

Quick Reference Card

Command	Result	Description
`x_1`	$x_1$	Single subscript
`x^2`	$x^2$	Single superscript
`x_{12}`	$x_{12}$	Multiple character subscript
`x^{2n}`	$x^{2n}$	Multiple character superscript
`x_i^j`	$x_i^j$	Combined sub/superscript
`\sum_{i=1}^n`	$\displaystyle\sum_{i=1}^n$	Summation limits
`\lim_{x \to 0}`	$\displaystyle\lim_{x \to 0}$	Limit notation
`f'(x)`	$f'(x)$	Prime notation
`{}_{a}^{b}X_{c}^{d}`	${}_a^b X_c^d$	Pre-superscript/subscript
`\textsubscript{2}`	H $_2$ O	Text mode subscript
`^{14}\mathrm{C}`	$^{14}\mathrm{C}$	Isotope notation
`T^{\mu\nu}_{\rho}`	$T^{\mu\nu}_{\rho}$	Tensor notation

Mathematical Expressions

Basic math mode and LaTeX subscript expressions

Equations Guide

Multi-line and numbered equations

Matrices & Arrays

Matrix notation with subscript indices

LaTeX Symbols Reference

Complete symbol reference for subscripts

Chemistry Notation

Chemical formula subscript notation

Physics Notation

Physics symbols and tensor notation

Try Subscripts and Superscripts

Open a math example

Paste the examples into a project and compile them to check braces, combined indices, and common error fixes.

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​What You’ll Learn

​Frequently Asked Questions

​Basic Syntax

​Subscripts (Indices)

Expected output

​Superscripts (Exponents)

Expected output

​Important Rule: Braces for Multiple Characters

​Combined Subscripts and Superscripts

​Basic Combinations

Expected output

​Nested Subscripts and Superscripts

​Special Use Cases

​Limits and Operators

​Chemical Formulas

Expected output

​Physics and Engineering Notation

Expected output

​Advanced Techniques

​Primes and Multiple Primes

Expected output

​Positioning and Spacing

​Accents with Sub/Superscripts

Expected output

​Text Mode Subscripts and Superscripts

Expected output

​Common Errors and Solutions

​Best Practices

​1. Readability Guidelines

​2. Consistency Rules

​3. Special Notation Standards

​4. Accessibility Considerations

​Quick Reference Card

​Related Topics

Mathematical Expressions

Equations Guide

Matrices & Arrays

LaTeX Symbols Reference

Chemistry Notation

Physics Notation

​Further Reading & References

​Try Subscripts and Superscripts

Open a math example

See the online LaTeX editor

What You’ll Learn

Frequently Asked Questions

Basic Syntax

Subscripts (Indices)

Superscripts (Exponents)

Important Rule: Braces for Multiple Characters

Combined Subscripts and Superscripts

Basic Combinations

Nested Subscripts and Superscripts

Special Use Cases

Limits and Operators

Chemical Formulas

Physics and Engineering Notation

Advanced Techniques

Primes and Multiple Primes

Positioning and Spacing

Accents with Sub/Superscripts

Text Mode Subscripts and Superscripts

Common Errors and Solutions

Best Practices

1. Readability Guidelines

2. Consistency Rules

3. Special Notation Standards

4. Accessibility Considerations

Quick Reference Card

Related Topics

Further Reading & References

Try Subscripts and Superscripts