mekso quaternary operator – Pochhammer symbol: with/for input (X_{1, X}, this word/function outputs \prod_{k }= 0^X_{2 - 1 (X}; by default, X_{4 }= 1 unless explicitly defined otherwise.

For the basic definition, all inputs (especially those which are not X_{1}) should be nonnegative integers; X_{3} can be further restricted to 0 (for the falling factorial) and 1 (for the rising factorial); X_{4 > 0} will be typical. X_{2 < 1} yields the empty product, which is typically defined by convention to be 1, regardless of all other inputs (so long as they are valid/belong to the domain). X_{2} is the number of terms in the aforementioned defining product and interacts with X_{4} in somewhat-complicated ways; be careful to avoid multiplying by nonpositive numbers unless such is actually desired (which may break certain recursive formulas); in order to avoid negative terms, enforce that X_{2 < 1 +} min(Set(1, X_{1 \% X}, where: "\%" denotes the modulus/remainder (see: "vei'u") of its left-hand/first input (here: X_{1}) wrt/when integer-dividing it by its right-hand/second input (here: X_{4}); recall: x \% y in [0, y) for all real numbers x and y: y > 0. Also, X_{4 }= 1 by default. See also: "ne'o", "ne'oi".

- gei'au
*(exp!)* - mekso 7-ary operator: for input (X
_{1 }= z, X_{2 }= (a_{i)}= (b_{j)}= p, X_{5 }= q, X_{6 }= h_{1, X}= h_{2)}, this word/function outputs/yields \sum_{n}=0^\infty (((\prod_{i }= 1^{p (}ne'o'o(a_{i,n,1,h}= 1^{q (}ne'o'o(b_{j,n,1,h}; by default, X_{6 }= 1 = X_{7}unless explicitly specified otherwise.