Number of żaden

[Kimmalyn]

Unlike każdy and wszystek (which stresses the individual and the group respectively, and therefore uses a singular and plural respectively), I find examples online that use both a singular and a plural noun after żaden:

(from linguee)
Nawet jeżeli nie istnieje żadna norma dla produktu, musi on być bezpieczny i spełniać wymagania bezpieczeństwa zawarte w [...]
Even if there does not exist any standard for the product,
vs
Osoby z UE powinny zadbać o to, by nie angażować się w żadne transakcje biznesowe sprzeczne z sankcjami unijnymi [...]
not to engage in any business transactions

Sentence 1 uses NOM sing. for norma, and
Sentence 2 uses ACC pl. for transakcja (angażować się w is a set phrase and takes ACC)

If both examples are negative and both instances of 'any' indicate 'not even one', why does one use singular and one plural? And what is the difference between these two usages?

Dziękuję bardzo!

[Stasia]

[mention]Kimmalyn[/mention], the answer is right there in the English translation. There has to be an agreement with the noun. The only difference is that każdy is used with singular nouns, wszystkie with plural nouns, and żadny can be used with all nouns, but each one of them needs to be in agreement with the noun:

żadna norma = any/no norm (singular feminine)
żadne transakcje = any/no transactions (plural feminine).

żaden człowiek = any man/no man (singular masculine)
żadni ludzie = no people (plural masculine)

żadne dziecko = no child (singular neutral)
żadne dzieci = no children (plural neutral)

Każdy also has to agree with the noun, but it's used with singular nouns:

Każda norma = each norm (singular feminine; note that the English word requires a singular verb, too)
Każdy człowiek = each man (singular masculine)
Każde dziecko = each child (singular neutral)

Wszystek - do you mean wszystkie? This is a case where we only use it with plural nouns:

Wszystkie transakcje = all transactions (plural feminine; note that the English word requires a plural verb, too)
Wszyscy ludzie = all people (plural masculine)
Wszystkie dzieci = all children (plural neutral)