JQuery :: Changing Css Properties Of One Element By Another

I have a billion elements that all share the same class. I have another billion elements that all share another class. This cannot be changed. My objective is to use one element to trigger onclick a change in the others elements' css properties, that is each element is paired with another, producing a billion unique pairs. From hours of deciphering the cryptic documentation examples ive come up with the following, which doesnt work. Assume that im using "name=item#" in the element's tag to identify each pair.

One fundamental issue with this is that it will change the opacity of both elements in the pair were both elements to share a name,or it will only affect the element being clicked on if not, but i only want it to change the opacity of the element that isnt being clicked. Another issue is that there are instances where i may need to set a setTimeout on a css property, and ive not found any documentation on integrating javascript and jquery together within a function.So how do i get this function to accept input from one element and affect the css properties of the other? And what would a setTimeout look like if it were placed around the opacity property?