1. Standard LaTeX symbols

The following tables show the standard symbols for LaTEX users.

TABLE I. Text accents with letter a.

à \`{a}  á \'{a}  â \^{a}  ä \"{a}
ã \~{a}  ā \={a}  ȧ \.{a}  ă \u{a}
ǎ \v{a}  a̋ \H{a}  aa \t{aa}  a̧ \c{a}
a. \d{a}        ā \b{a}

TABLE II. Math accents with letter a.

â \hat{a}     ǎ \check{a}   ȧ \dot{a}     ä \ddot{a}
ă \breve{a}   ã \tilde{a}   à \grave{a}   á \acute{a}
ā \bar{a}     a⃗ \vec{a}

TABLE III. Special symbols; any mode.

† \dag  § \S              \begin{matrix}c \\ ◯ \end{matrix} \copyright
‡ \ddag  ¶ \P  £ \pounds

TABLE IV. Other special (foreign) symbols; text mode.

å \aa  Å \AA  æ \ae  Æ \AE
ø \o  Ø \O  œ \oe  Œ \OE
ł \l  Ł \L  ¿ ?`  ¡ !`
ß \ss

TABLE V. Greek letters; used in math mode. Lowercase

α \alpha  β \beta  γ \gamma  δ \delta
ϵ \epsilon ε \varepsilon ζ \zeta  η \eta
θ \theta  ϑ \vartheta  ι \iota  κ \kappa
λ \lambda μ \mu  ν \nu  ξ \xi
o o  π \pi  ϖ \varpi  ρ \rho
ϱ \varrho σ \sigma  ς \varsigma τ \tau
υ \upsilon ϕ \phi  φ \varphi  χ \chi
ψ \psi  ω \omega

Uppercase

Γ \Gamma  Δ \Delta  Θ \Theta  Λ \Lambda
Ξ \Xi  Π \Pi  Σ \Sigma  Υ \Upsilon
Φ \Phi  Ψ \Psi  Ω \Omega

TABLE VI. Binary operation symbols; used in math mode.

± \pm  ∓ \mp  × \times ÷ \div
∗ \ast  ⋆ \star  ∘ \circ • \bullet
∩ \cap  ∪ \cup  ⊎ \uplus · \cdot
⊓ \sqcap  ⊔ \sqcup ∨ \vee  ∧ \wedge
⊕ \oplus  ⊖ \ominus ⊗ \otimes ⊘ \oslash
△ \bigtriangleup ⊙ \odot  < \lhd  † \dagger
▽ \bigtriangledown ◯ \bigcirc > \rhd  ‡ \ddagger
◁ \triangleleft  ⋄ \diamond ≤ \unlhd \ \setminus
▷ \triangleright ≀ \wr  ≥ \unrhd ⨿ \amalg

TABLE VII. Relation symbols; used in math mode.

≤ \leq  ≥ \geq  ≪ \ll  ≫ \gg
≡ \equiv  ≍ \asymp  ≠ \neq        ≐ \doteq
⊂ \subset ⊃ \supset ⊆ \subseteq ⊇ \supseteq
⊏ \sqsubset ⊐ \sqsupset ⊑ \sqsubseteq ⊒ \sqsupseteq
⊧ \models ⊥ \perp  | \mid  ∥ \parallel
≺ \prec  ≻ \succ  ⪯ \preceq  ⪰ \succeq
∼ \sim  ≃ \simeq  ≈ \approx     ≅ \cong
▷◁ \bowtie ⋈ \Join  ⌣ \smile  ⌢ \frown
∈ \in  ∋ \ni  ⊢ \vdash  ⊣ \dashv
∝ \propto

Negated relations can sometimes be constructed with \not. For example,

      If $x \not< y$ then $x \not\leq z$.

gives

If x ≮ y then x ≰ z.

TABLE VIII. Arrow symbols; used in math mode.

← \leftarrow  → \rightarrow
⟵ \longleftarrow  ⟶ \longrightarrow
⇐ \Leftarrow  ⇒ \Rightarrow
⟸ \Longleftarrow  ⟹ \Longrightarrow
↩ \hookleftarrow  ↪ \hookrightarrow
↼ \leftharpoonup  ⇀ \rightharpoonup
↽ \leftharpoondown  ⇁ \rightharpoondown
⇀ ↽ \rightleftharpoons  ⇝ \leadsto
↔ \leftrightarrow  ⟷ \longleftrightarrow
⇔ \Leftrightarrow  ⟺ \Longleftrightarrow
↦ \mapsto  ⟼ \longmapsto
                  ↑ \uparrow
                  ↓ \downarrow
                  ⇑ \Uparrow
                  ⇓ \Downarrow
                  ↕ \updownarrow
                  ⇕ \Updownarrow
                  ↗ \nearrow
                  ↘ \searrow
                  ↙ \swarrow
                  ↖ \nwarrow

TABLE IX. Miscellaneous symbols; used in math mode.

♭ \flat  ♮ \natural ♯ \sharp  ′ \prime
\ \backslash  ∀ \forall ∞ \infty  ∃ \exists
∅ \emptyset  □ \Box  ∇ \nabla  ¬ \neg
◇ \Diamond  √ \surd  △ \triangle ∥ \|
♣ \clubsuit  ℵ \aleph  ℘ \wp  ⊤ \top
♢ \diamondsuit ℜ \Re  ℓ \ell  ⊥ \bot
♡ \heartsuit ℑ \Im  ı \imath  ∂ \partial
♠ \spadesuit  h̄ \hbar  ȷ \jmath     ^{}\angle
℧ \mho

TABLE X. Log-like functions; used in math mode.

\arccos    \arcsin    \arctan    \arg     \cos
\cosh      \cot       \coth      \csc     \deg
\det       \dim       \exp       \gcd     \hom
\inf       \ker       \lg        \lim     \liminf
\limsup    \ln        \log       \max     \min
\Pr        \sec       \sin       \sinh    \sup
\tan       \tanh

TABLE XI. Delimiters; used in math mode.

( (  ) )  / /
[ [  ] ]  \ \backslash
{ \{  } \}  | |
⟨ \langle  ⟩ \rangle  ∥ \|
↑ \uparrow  ⇑ \Uparrow  ⌊ \lfloor
↓ \downarrow  ⇓ \Downarrow  ⌋ \rfloor
↕ \updownarrow  ⇕ \Updownarrow  ⌈ \lceil
                                        ⌉ \rceil

TABLE XII. Miscellaneous symbols; used in math mode.

∑ ∑ \sum  ∏ ∏ \prod  ∐ ∐ \coprod
∫ ∫ \int  ∮ ∮ \oint  ⨄ ⨄ \biguplus
⋂ ⋂ \bigcap ⋃ ⋃ \bigcup  ⨆ ⨆ \bigsqcup
⨀ ⨀ \bigodot ⨂ ⨂ \bigotimes ⨁ ⨁ \bigoplus
⋁ ⋁ \bigvee ⋀ ⋀ \bigwedge

2. Standard LaTeX typefaces

You can access a pair of special typefaces in LaTEX. You can switch to script (calligraphic) letters by using

the \cal command (note the L):

{\cal L}_{\text{int}} = e F^{3}_{\pi} r^{2}
  B^{0}(r,t) \epsilon \sin(\Omega t)
  \exp(\eta t),

gives

L_{int} = eF_{π}^{3}r^{2}B^{0}(r, t)ϵ sin(Ωt) exp(ηt),

Only uppercase letters are available in the \cal font.

You can switch to sans serif letters by using the \sf command (note the M):

R({\cal Q}-{\cal Q}_{0})
=R_{0} \exp\left(-\frac{1}{2}\Delta {\cal Q}
 \cdot{\sf M}\cdot\Delta{\cal Q}\right).
  \label{eq:rdef}

gives

R(Q − Q_{0}) = R_{0} exp (−\frac{1}{2}ΔQ · M · ΔQ) .

Both uppercase and lowercase letters are available with

\sf.

3. Other notations

The \overline command puts a horizontal line above its argument in math mode:

$\overline{x}+\overline{y}$

gives

\overline{x} + \overline{y}

There is an analogous \underline command that works in text or math mode:

The equation \underline{is} $\underline{x+y}$.

gives

The equation \underline{is} \underline{x + y}.

Horizontal braces are put above or below an expression

with the \overbrace and \underbrace commands:
$\underbrace{a_{1} + \overbrace{a_{2}+a_{3}}
  + a_{4}}$

gives

\underbrace{a_{1} + \overbrace{a_{2} + a_{3}} +a_{4}}

and in displayed math, a subscript or a superscript puts a label on the brace:

$\underbrace{a_{1} +
  \overbrace{a_{2}+\cdots+a_{n-1}}^{n-2}
   + a_{n}}_{n}$

gives

\underbrace{a_{1} + \overbrace{a_{2} + ⋯ + a_{n−1}}^{n−2} +a_{n}}_{n}

Wide versions of the \hat and \tilde commands are available. They are called \widehat and \widetilde, respectively. Here is an example:

$\widehat{a} + \widehat{ab}
 + \widehat{abc} + \widehat{abcd}$

gives

â + âb + âbc + âbcd