We examine how the digit 9 organizes patterns in base-10 exponential decay sensitivity. From the relation ∆ = −ln(2)/10r2, inputs involving 9, π, and 11 yield outputs that cluster near multiples of 9/π and √10. We introduce the Enneadic Sensitivity Transform and show that 9 functions as a stabilizing element in decimal arithmetic. To 9 decimal places, any input is drawn into the 9-10-π structure. We interpret 10 as a positional marker that denotes completion of the 9-digit cycle, with 10 ≡ 1 (mod 9). This suggests base-10 functions as base-9 with a carry notation.
Nicolas Antony Brown (Wed,) studied this question.