Lost in Translation: Harmonizing Terminology and Defining Mathematical Tools for Panel Optimization

ABSTRACT Spectral flow cytometry has evolved from a contentious idea into a mainstay of high‐parameter single‐cell analysis, yet its vocabulary (and the statistical reasoning behind it) remains a patchwork of overlapping, sometimes contradictory terms. This position paper highlights the terminological fragmentation and translation gap, and aims to harmonize the field's lexicon while providing a cohesive information‐theoretic framework for panel optimization. We expose the limits of popular ad hoc heuristics, matrix condition numbers, and pairwise cosine similarities, and promote stronger surrogates: effective rank and information efficiency, which together capture spectral independence and numerical stability, and the Cramér–Rao lower bound (CRLB) matrix, which directly predicts fluorochrome‐specific spreading error. Building on this foundation, we revive the optimal‐design criteria: D‐optimality maximizes total information; A‐optimality minimizes the average parameter variance; E‐optimality constrains worst‐direction inflation. By aligning precise definitions with actionable design rules, we provide a roadmap for consistent terminology, next‐generation panel construction, and objective instrument benchmarking.