Which case is the noun dog in when you approach it? - briefly
The noun "dog" is in the accusative case when you approach it. This is because the action of approaching requires a direct object, which in Russian grammar is marked by the accusative case.
Which case is the noun dog in when you approach it? - in detail
When approaching a dog, the noun "dog" is typically in the accusative case if you are considering it as the direct object of an action verb. For example, in the sentence "I see a dog," the noun "dog" is in the accusative case because it is the object that receives the action of seeing. However, if the context changes and the dog is not directly involved in the action, such as in "There is a dog near me," then the noun "dog" would be in the nominative case, serving as the subject of the sentence. It's crucial to understand the grammatical role the noun plays within the sentence structure to determine the correct case.