The Noun

There are countable and uncountable nouns.
Countable
a chair
a question
an engineer
a bus
Uncountable
mater
milk
freedom
friendship

The countable noun is used in the form of the singular and the plural.
The uncountable nouns is used only in the form of singular.

Some nouns form the plural by changing the root vowel.

The plural of the nouns sheep, deer, swine and fish is identical with the singular.

Some nouns borrowed from Latin and Greek keep the plural form of the language from which they have been borrowed.
A phenomenon [finominen]-phenomena [finimine]явище
a crisis [ kraisis ]-crises[kraisiz]
a radius [reidjes]-radii [reidiai]

If the singular ends in – th [θ] preceded by a long vowel or a diphthong, in the plural the final [θ] is changed into [ ʆ] after which the ending –s is pronounced [z].
A path [pa:θ]- paths [pa:ʆz]

Some nouns ending in – o
take –es.
f.e Tomato- tomatoes
But:
radio-radios, piano- pianos,
photo- photos, video- videos.

Repeat the rule!

Plurals
Spelling Rules
To form plural nouns we usually add -s to the noun.
one pen - two pens
Nouns ending in -s, -ss, -ch, -x or -o take -es in the plural.
bus - buses, glass - glasses, brush - brushes, watch - watches, fox - foxes, tomato - tomatoes
However, some nouns ending in - o take only –s .
radio - radios, piano - pianos, studio - studios , video - videos kilo - kilos
Nouns ending in a vowel + y take -s in the plural.
boy - boys
Nouns ending in a consonant + y drop the -y and take -ies in the plural.
party - parties , baby - babies
Most nouns ending in -f or -fe, drop the -f or -fe and take -ves in the plural.
knife - knives , wolf - wolves
However, some nouns ending in -f or -fe take only -s.
roof - roofs, cliff - cliffs, giraffe - giraffes

Irregular Plurals
Some nouns do not form their plural according to the about rules.
They either have a different form or the same form as in the
singular.
These are:

Countable / Uncountable Nouns
Countable nouns are nouns which we can count. They have singular and plural forms.
One egg, two eggs, three eggs

Uncountable nouns are nouns which we cannot count. Uncountable nouns have only
singular forms. These nouns include:
Food: cheese, butter, salt, pepper, bread, spaghetti, etc
Liquid: coffee, milk, water, tea, lemonade, etc

We can use the following nouns before uncountable nouns to show quantity: