An AI system analyzes patient visit summaries to predict condition severity. The entire process is modeled by the expression $s(\bar{\mathbf{y}}_1 \dots \bar{\mathbf{y}}_k)$. The system first divides a summary into $k$ sections (e.g., 'Symptoms', 'Diagnosis'). For each section, it computes a vector representing the average semantic meaning of the text within it. Finally, the function $s$ processes the sequence of these vectors to output a severity score. In this specific context, what does a single term $\bar{\mathbf{y}}_i$ represent? Explain the significance of both the overbar ( ¯ ) and the bold font in your answer.