1. Some nouns are always used in singular. These are uncountable nouns. We should not use article ‘a’ and ‘an’ with such nouns. These nouns are scenery, furniture, stationary, wastage, jewellery, knowledge, money, business, breakage, food luggage, poetry, machinery, traffic iron, electricity, crockery etc.
(i) He has no knowledge of grammar.
(ii) She takes her jewellery from a hallmark shop.

2. Some nouns look singular but have plural meaning such nouns take plural verbs. These are cattle, clergy, poultry, polices, people, infantry etc.
(i) Cattle are grazing in the field.
(ii) Police have arrested the thieves.

3. Some nouns always remain in plural form. They take plural verb. These nouns have no singular form. These are ashes, appears, goggles, eyeglasses, binoculars, vegetables, wages, species, scissors, fireworks, belongings, spectacles, tongs, surroundings etc.
(i) We should always buy fresh vegetables.
(ii)Binoculars help us to see distant objects clearly.

4. Some nouns look plural in from but have singular meaning. Some nouns take singular economics, ' politics, civics, innings, measles etc.
(i) I am quite good in Mathematics.
(ii) Ethics demands honesty in working.

5. Some nouns have the same form in singular as well as in plural.
e.g., deer, sheep, means, team, family, aircraft, Jury, crew
(i) There are four team in this tournament.
(ii) Our team win the match.

6. Some nouns have plural meaning. If a definite numeral adjective is used before them they are not pluralized.
eg, dozen, hundred, thousand, million, billion, score, gross, pair etc.
(i) This shirt costs three hundred rupees only.
(ii) She bought two pair of socks.

7. If the same noun is repeated after preposition, the noun will be singular.
e. g.,
Row upon row of pink marble looks beautiful.

8. Some nouns are used for specifically for feminine gender only e.g., maid, midwife, Virgin etc.
9. Some nouns are known as common gender nouns. They can be used for either male or female. These are called dual gender nouns.

Such nouns are teacher, student, child clerk, candidate, politician, neighbour, person, client, writer, author, leader, advocate, musician worker, enemy, president etc.when these are used in singular, use third person singular masculine (his but not her) pronoun with then.
(i) No one should abuse one’s worker.
(ii) Every candidate should use his voting right.