Notationally, parantheses seem to be very popular. Almost too popular. The following is a collection of all the different notations that I've found paranthesis used for. If you would like to add one, send me a pull request on Github.
| Name | Usage | Locations (non-exhaustive) |
|---|---|---|
| Function application | The value $f(2)$ is, oddly, ... | Mathematics, programming |
| Precedence | $2+(3\cdot5) \neq (2 + 3) \cdot 5$ | Mathematics, programming |
| Parentheticals | The man (who wore flannel) began ... | Writing |
| Ideal | $(N) := \{kN \mid k \in \mathbb Z\}$ | Ring Theory |
| Tuples | $(x,y)=(0.5, 1.7)$ | Mathematics, programming |
| Indexing | item = my_list(i) | MATLAB |
| $n$-dimensional sequences | Consider the sequence $(a_{ij})$ ... | Mathematics |
| Multiplication | $(5)(17) = 85$ | Mathematics |
| S-Expression | (f x y z) | Lisps |
| Interval notation | ...so for any $x$ in $[0, +\infty)$ we have ... | Mathematics |
| $n$ choose $k$ | ${n \choose k} = \frac{n!}{k!(n-k)!}$ | Mathematics |
| Matrices | $I_2 := \left( \begin{matrix} 1 & 0 \\ 0 & 1 \end{matrix} \right)$ | Mathematics |
| Greatest common divisor | $(a, b) := \mathit{gcd}(a, b)$ | Mathematics |
| Generator expression | (f(x) for x in li) | Python |
| Function shorthand | (+), (+2), (3*) | Haskell |
| Congruence | $5 \equiv 15\ (\text{mod } 10)$ | Mathematics |
| Labels | See example (B) or refer back to (II) to... | Writing |
| Unit | () | Haskell |
| Enumeration | Two things: 1) ...; and 2) ... | Writing |
| Emojis | :) :( ;) :'( | Texting |