When to use "the" in numbering and labelling? [closed]

Edit I have completely rewritten this answer, because what I wrote first (about the context), though accurate, was not in fact the answer to the question. Thank you for calling me on it, @homocomputeris.

This form without "the" is used only when the item is one of a set of [noun]s which are distinguished by the letter or number: the combination of [noun] and the label act as the name, but you couldn't (usually) use just the label without the noun.

So your "method" example would work, if there was a recognised list of methods referred to as X, Y, Z ... (either in the present document, or in the field at large).

It's possible that "variable x" might be used that way, but I'm not sure.

The "name" and "words" examples do not work, though.