Differentiated nouns

number) changes the semantic meaning of a word.

singular will be understood as simply "one", as opposed to

the meaning of the plural as "many" in the sense of "more than one".

This is apparently obvious for such correlations as book — books, lake — lakes and the like.

and singulars that cannot be fully accounted

for by the above ready-made approach.

as

potato (one item of the vegetables) and potatoes (food), paper (material) and papers (notes or documents), sky (the vault of heaven) and skies (the same sky taken as a direct or figurative background), etc.

broader sememic mark of the plural, or "plurality" in the

grammatical sense, should be described as the potentially dismembering reflection of the structure of the referent,
while the sememic mark of the singular will be understood as the non-dismembering reflection of the structure of the referent, i.e. the presentation of the referent in its indivisible entireness.

plural forms that differ from one another in their plural

quality as such. The extreme point of this semantic scale is marked by the lexicalisation of the plural form, i.e. by its serving as a means of rendering not specificational, but purely notional difference in meaning.
Cf. colours as a "flag", attentions as "wooing", pains as "effort", quarters as "abode", etc.

increase to such a degree that the plural form develops

a completely new meaning which the singular has not got at all. Thus, for example, the plural form colours has the meaning 'banner' which is restricted to the plural (e. g. to serve under the colours of liberty). In a similar manner, the plural attentions has acquired the meaning 'wooing' (pay attentions to a young lady).
Since, in these cases, a difference in lexical meaning develops between the plural and the singular, it is natural to say that the plural form has been lexicalised.
What is essential from the grammatical viewpoint is the very fact that a difference in meaning which is purely grammatical in its origins is apt under certain conditions to be overshadowed by a lexical difference.”

like I was nuts.
The bizarre rantings in the notes left

behind by the serial killer convinced the police that these guys were nuts.