Usually the latin letters $i,j,k,l,m,n$ are used as indexes in sequences or sets with $k$ elements ($A = \{ a_1,...,a_k \} $). But when we already used all these letters is there any recommendation? Are there any greek letters that are commonly used with the same purpose?
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$\begingroup$ May I ask in what context you get so many sets with disjoint cardinalities? I also use $p,q$ in some situations. $\endgroup$– AlexRJul 23, 2014 at 19:02
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1$\begingroup$ In older literature $\nu$ is often used to index sequences and summations. $\endgroup$– Dave L. RenfroJul 23, 2014 at 19:15
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$\begingroup$ @AlexR, sure, multidimensional sequences. So, $n$ and $m$ are the sizes and $i$ and $j$ the general terms of two sequences, $l$ the number of dimensions and $k$ the general term to refer the dimensions :/. $\endgroup$– user136913Jul 23, 2014 at 19:32
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$\begingroup$ @user136913 Maybe consider using uppercase letters corresponding to the indices as the size? $(a_m)_{m=1}^M$ for example. $\endgroup$– AlexRJul 23, 2014 at 19:33
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$\begingroup$ @AlexR, I'm using the capital letters for the sequences and sets, but I'm going to try this to see how it looks, thanks! $\endgroup$– user136913Jul 23, 2014 at 19:49
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2 Answers
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Commonly I use the following letters as indices:
$$\text{Discrete}: i,j,k,l,m,n,p,q,r,s\\
\text{Continuous}: \alpha, \beta, t, \epsilon$$
And these as sizes of discrete sets:
$$K,l,L,m,M,n,N,P,Q,r,R,s,S$$
That's of course opinion based, but these are my favorites and $m,n$ only when not in use as an index.
$r,s$ occur as sizes mostly in numerical context (quadrature formulas / interpolation degree) and $l$ mostly as the "level" of recursion or iteration in an algorithm.
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The letters $\alpha$ and $\beta$ are common for indices.
answered Jul 23, 2014 at 18:59
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$\begingroup$ Haven't seen any of those as indicators for the maximum index, though... $\endgroup$– AlexRJul 23, 2014 at 19:00
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$\begingroup$ @AlexR I have, but as maximum index is uncommon. As a mere index, on the other hand, it's common. $\endgroup$ Jul 23, 2014 at 19:16
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