Step 1: Chromosome arrangement is defined as the quantity and structure of chromosomes in a cell. Euploidy signifies the standard condition where an organism possesses the correct chromosome count, comprising a complete set.
Step 2: Definitions of terms.
Monoploidy (Option A): Cells characterized by a single chromosome set (\(n\)), observed in certain specialized organisms but absent in typical diploid organisms.
Aneuploidy (Option B): An abnormal chromosome count resulting from the acquisition or deletion of particular chromosomes (e.g., trisomy, monosomy).
Polyploidy (Option C): Organisms possessing more than two complete sets of chromosomes (\(3n, 4n\)), prevalent in plants but not characteristic of humans.
Euploidy (Option D): Organisms exhibiting the correct and complete chromosome count in multiples of a foundational set (\(2n\) in diploids), denoting the typical state.
Step 3: Summary.
Euploidy is the designation for the standard chromosome arrangement within organisms. \[ \therefore \text{The correct answer is: Euploidy.} \]