Final answer:
The sentence given indicates the function of balls, as it describes what the balls are used for in the context of the sentence, which is playing games.
Step-by-step explanation:
The sentence "We play games with balls" indicates the function of the balls. In English grammar, understanding how parts of speech function in sentences is essential. The function refers to how words are used within the context of a sentence, which might differ from their basic form or meaning when analyzed in isolation. In this sentence, the balls are used for playing games, which is their function in the context of this activity.