The singular and plural forms of a noun are marked by adding or not adding the suffix “-lar, -ler” : nouns to which the suffix “-lar/ -ler” has not been added are considered to be the singular form of the noun, while nouns to which the suffix “-lar/ -ler” has been added are considered to be the plural form of the noun. For example:
kitab — kitablar (book — books)
depter — depterler (notebook — notebooks)
sheher — sheherler (city — cities)