Find the dissimilar word from the following options:
$$\text{R54, W68, U63, L36, Y75}$$

Let's discover the hidden relationship between the letter and the number in each pair by using the alphabetical positional values of the letters ($\text{A}=1,\text{B}=2,\dots ,\text{Z}=26$):
* R54: $\text{R}=18\to 18\times 3=54$
* U63: $\text{U}=21\to 21\times 3=63$
* L36: $\text{L}=12\to 12\times 3=36$
* Y75: $\text{Y}=25\to 25\times 3=75$
* W68: $\text{W}=23\to 23\times 3=69$ (but the given value is $68$)

The pattern is that the number is equal to three times the positional value of the corresponding letter. The pair W68 violates this rule. Thus, it is the dissimilar word.