If x and y are names for scalars and you wish to use them as a list, then (x,y) is the answer, as several here have already said.
In J, however, it's common for nouns to be non-scalar values. Whether they can be simply joined is not something that can be answered in general. What we can say is that when multiple nouns are combined structurally the result will be a regular (non-ragged) array of homogenous atomic type. The pattern by which that result is processed will depend on the rank of the verb that's processing it. Those units-of-processing might correspond to the pieces that were previously put together, but it might not. That's something a J programmer has to manage. When you see numbers in sequence being treated as a list, it's helpful to think of that list-making as a *lexical* feature of J. Directly expressed numeric nouns treat internal whitespace as a separator between list items, and this special interpretation of whitespace has higher precedence than the meaning of whitespace between tokens in a J sentence. Because of this, a sequence of numbers forms a single token. That parsing rule is a convenience that allows us to skip having the equivalent of quotation marks, such as we use for text values. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
