I've been looking for the antonym of dense. I'm looking for an exact opposite: a single word the means, precisely, "having less mass per unit volume than another object".
That is, I'm seeking a scientific word which could be put into this sentence, and have it make sense:
Wood is more
To mean precisely the opposite of:
Metal is denser than wood
And precisely the same as:
Wood is less dense than metal
Only using a single word (as an atomic comparative), as opposed to the two words "less dense".
As analogies, we have the pairs "heavy"/"light" and "thin"/"thick", and thus needn't to resort to circumlocutions like "more massive" or "less wide".
For similar reasons, I find "light" (the opposite of "heavy") and "spread out" (the opposite of "congested", i.e. "smaller population per unit volume") unsatisfying. I would like a single, atomic word that enjoys some currency in scientific prose, which means precisely "less mass per unit volume".