Sentence:  Soon after the first law of thermodynamics was postulated in the mid nineteenth century, it was realized how the law presupposed a more elementary law, which we now call the zeroth law ... But scientists soon realized how even the zeroth law was too advanced, since it presupposed a yet more elementary law, which explains why the minus-<WSD>oneth</WSD> law had to be formulated. 
Meaning of the word marked with <WSD> tags:  'first', or other ordinal derivatives of 'one', such as "hundred-and-oneth" or "minus-oneth"