Questions & Answers about Мой внук гуляет в парке.
Внук is grammatically masculine and most often means grandson.
- внук = grandson
- внучка = granddaughter
- внуки = grandchildren (can be mixed or all of one gender)
In everyday speech, внук is usually understood specifically as a male grandchild, unless the context clearly makes it generic.
In Russian, possessive words like мой (my) agree in gender, number, and case with the noun they modify.
Внук is masculine singular, so you must use the masculine singular form мой.
Basic nominative forms of my:
- мой – masculine (мой внук – my grandson, мой брат – my brother)
- моя – feminine (моя внучка – my granddaughter, моя мама – my mom)
- моё – neuter (моё письмо – my letter)
- мои – plural (мои внуки – my grandchildren)
So мой внук is correct because внук is masculine.