Differentiated nouns

Differentiated nouns are nouns where ending -s (in plural number) changes the semantic meaning of a word.

On the surface of semantic relations, the meaning of the 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.

However, alongside of these semantically unequivocal correlations, there exist plurals and singulars that cannot be fully accounted for by the above ready-made approach.

This becomes clear when we take for comparison such forms 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.

As a result of the comparison we conclude that the 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.

On the other hand, there are semantic varieties of the 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.

Ilyish says that “the difference between the two numbers may 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.”

Some examples
of
differentiated nouns

Address
обращение; речь; официальное выступление
Addresses
(уст.) ухаживание

Arm
рука
Arms
вооружение
военная служба
война

Board
доска
Boards
подмостки, сцена; сценическая профессия

Bone
кость (часть скелета позвоночных)
Bones
скелет; костяк;
человек; тело
останки, мощи

Element
хим. элемент
элемент, составная часть
Elements
основы, азы
непогода (ветер, дождь)

Fundamental
основное правило; принцип
Fundamentals
основы

Gut
кишка; (разг.) брюхо
Guts
(разг.) внутреннее
cодержание
(разг.) мужество,
характер, сила воли

Head
голова
Heads
руда
лицевая сторона
монеты (с изображением головы), орёл

Heart
сердце, душа
Hearts
черви (масть)

ill
вред, зло
ills
неприятности, проблемы

iron
железо
irons
кандалы, оковы

Kennel
собачья конура
свора собак
Kennels
псарня;
собачий питомник

Land
земля, суша
почва
страна; государство
Lands
поместья

Legality
законность; легальность
следование закону
Legalities
обязательства, налагаемые законом

Letter
буква
письмо
Letters
литература

Liberty
свобода
Liberties
(юр.) вольности, привилегии

Light
свет; освещение
Lights
мнение, оценка; система принципов

Line
линия, черта, штрих
строка
контур
экватор
Lines
план, чертеж
строй (солдат)
стихи, поэзия

Manner
манера, поведение
Manners
воспитанность, умение себя вести

Occasion
случай, событие
Occasions
(уст.) дела

Point
точка, пункт
вопрос
Points
достоинства, преимущества
пуанты