The word for today, "dermatoglyphics," got me thinking about adjectives used as nouns. As with words such as "optics" and "metrics," an adjective can be used as a noun when it is referring to a field of study; however, dermatoglyphics are also the subjects studied within this field. My instinctual reaction is to want to use “dermatoglyphs” as the plural noun. In my work life I rail against the use of such things as "deliverables" to describe the product we will deliver. Am I wrong? Is there a rule in English to govern the use of adjectives as nouns, or is it simply inherited on a case-by-case basis?

adjectives used as nouns

I bow to the collective will--I've been using "collectibles" all my life without a second thought! Thanks tsuwm.

Is it still an adjective when you stick an S on the end?

The s makes it one of the nounifiables.

Ah. Thanks for splainin me.

To Roman grammarians there were two kinds of nouns (Latin nomen, nomina, 'name; noun'): substantives (nomina substantiva) and adjectives (nomina adjectiva). Later English grammarians basically split the category of nomen into substantives (later called simply nouns) and adjectives. The distinction in Roman grammar had to do with nouns adjective being declined in the same manner as nouns substantive. Of course, it is interesting to note that both substantive and adjective started our as adjectives.