Učivo

changes of hard consonants into soft ones

Some consonants as "k; h; ch; (r;..) while we decline them change into their "softer" sounding counterparts as "c; z; š; (ř;..) 

It happens fo example with plural form of hard group of masculine animate "pán" 

pták -ptáci
major - majoři
jinoch - jinoši

and so on ... 

Proceeding with declination - the original "hard" consonant returns in genitiv; dativ; akuzativ and instrumental. 
Zasekli jste se? Řešení je zde
1 / 1

softening of consonants

zákazníci (customers)
právníci (lawyers)
ptáci
vrazi (murderers) 
bozi (gods)
partneři
bratři
hoši (boys)

DATIV: -kům

DATIV: -hům

DATIV: -rům

DATIV: - chům