Semantics

chest
Он лениво почесал себе грудь. He casually scratched his chest.
breast
Попугай с серьёзным видом чистил пёрышки у себя на груди. The serious-looking parrot groomed its breast feathers.
bosom
Она прижимала к груди какой-то свёрток. She clasped some sort of bundle to her bosom.
This entry is concerned with the use of the word грудь to refer to the part of a human or animal body that extends from the neck to the stomach. Common sense will dictate which of the expressions in this entry can or cannot be used to refer to animals.

The word грудь is also used to refer to each of the two breasts on a woman's body, or to a woman's bosom, i.e. to both breasts seen as a single shape. This usage is described in a separate entry. The word грудь is also used to refer to the part of clothing that covers the chest; this usage is not described in this dictionary. The meaning "imaginary seat of emotions" (И вдруг он почувствовал такую тоску в груди! "And suddenly he felt such anguish in his bosom!") is not described in this dictionary.