Pochhammer[a, n] gives the Pochhammer symbol (a) n.
PopupMenu[x, {val_1, val_2, ...}] represents a popup menu with setting x and possible values val_i. PopupMenu[Dynamic[x], {val_1, ...}] takes the setting to be the ...
PowersRepresentations[n, k, p] gives the distinct representations of the integer n as a sum of k non-negative p\[Null]^th integer powers.
Protect
(Built-in Mathematica Symbol) Protect[s_1, s_2, ...] sets the attribute Protected for the symbols s_i. Protect["form_1", "form_2", ...] protects all symbols whose names match any of the string patterns ...
QFactorial[n, q] gives the q-factorial [n] q!.
QGamma
(Built-in Mathematica Symbol) QGamma[z, q] gives the q-gamma function \[CapitalGamma]_q (z).
RankedMax[list, n] gives the n\[Null]^th largest element in list.
p .. or Repeated[p] is a pattern object that represents a sequence of one or more expressions, each matching p. Repeated[p, max] represents up to max expressions matching ...
expr /. rules applies a rule or list of rules in an attempt to transform each subpart of an expression expr.
Replace
(Built-in Mathematica Symbol) Replace[expr, rules] applies a rule or list of rules in an attempt to transform the entire expression expr. Replace[expr, rules, levelspec] applies rules to parts of expr ...