The word explain is a verb. Verbs do not have plurals; only nouns (and pronouns) have plural forms.
There is no plural form for the word, countries. This word itself is a plural.
The plural of diary is diaries.
The plural form of the word gelato is gelati.
The plural form of the word 'deed' is 'deeds'.
The plural form of the word neurosis is "neuroses".
The plural form for the demonstrative pronoun this is these.
The plural form of the word inferno is infernos.
The plural form is ranches.
There is no plural word for if.
There is no plural form for the word, countries. This word itself is a plural.
The plural form is data.
The plural form of the word "baby" is "babies."
The plural form for the word 'pioneer' is pioneers.
The plural form of the word "pharynx" is "pharynges."
The plural form of vow is vows.
There is no 'plural form' of the word 'minute'. The word is both singular and plural.
The plural form for the noun valley is valleys.