To determine the probability of selecting the letter 'A' from the given letter tiles (H, O, N, E, S, T), we first recognize that 'A' is not included in the set of tiles.
The total number of different letter tiles is 6 (H, O, N, E, S, T), and since 'A' is not one of them, the number of favorable outcomes for selecting 'A' is 0.
The probability \( P \) of selecting 'A' can be calculated using the formula:
\[ P(A) = \frac{\text{Number of favorable outcomes}}{\text{Total number of outcomes}} = \frac{0}{6} = 0 \]
Therefore, the probability of selecting the letter 'A' is:
0