The number of nouns.
Plural form nouns denoting the objects that can be counted as separate units. Such nouns are called conditionally countable.

Fast SQL database recovery sqlrecoverysoft.com - software.

Singular:
Book, roof, day, friend.
Education plural nouns.

Free recovery toolbox recoveryforsqlserver.com - for SQL Server 2005

The usual method of forming the plural of nouns - this is the end of the addition of - (e) s to the singular.
Plural:
Books, roofs, days, friends

Fast and effective software tool mdfrecoverytool.com - for a recovering MDF files of Microsoft SQL Server.

[S] after voiceless consonants sounds:
book books
text texts
lamp lamps
roof roofs
The plural
 - (E) s pronounced:
Safe-safes
- | Z | after voiced consonants and vowels:
Bags; days
| Tzl after hissing and whistling:
Singular:
Dress, box, dash, branch.
If the noun in the singular ends in-s,-ss,-xt-sh,-ch, i.e., hissing or whistling, then added the ending-es.
Plural.
Note.
Some nouns ending in the singular and in-fe-f, take the plural ending - (c) s, where f is transformed into v:
wife wives
life lives
half halves
shelf shelves
The same alternation of voiced and voiceless consonant in the formation of plural forms occurs in the noun house (units h) - houses (pl.).
Dresses, boxes, dashes, branches.
If the letter is preceded by a vowel, then added the ending-s, and have not changed:
way, - ways; key-keys
boy boys.
. In English, some nouns have kept up to date, the ancient form plurals by adding end-en, or by changing the root vowel:
Singular Plural
Man,-men
woman-women
child - children
ox-oxen
foot-feet
goose-geese
tooth-teeth
mouse-mice
. Some nouns have retained the ancient plural form, which coincides with the singular form:
Singular Plural
sheep
deer
swine
. Some nouns of Latin and Greek origin, retained the Latin or Greek plural form:
Singular Plural
basis bases
crisis crises
analysis analyses
thesis theses
axis axes