Which mood is used in the sentence "They are going to the ball game"?

The sentence "They are going to the ball game" is in the indicative mood. This mood is used to make factual statements or ask questions about reality. It conveys information or expresses an assertion. In this case, the sentence clearly states a fact about what "they" are doing—going to a ball game.

The indicative mood is the most commonly used mood in English and is characterized by straightforward declarations. It does not imply any command (which would fall under the imperative mood), nor does it express hypothetical situations or wishes (which are qualities of the subjunctive mood). The infinitive mood does not apply here as it generally refers to the base form of the verb, often preceded by "to," and does not constitute a complete sentence on its own.

Thus, it is clear that the indicative mood accurately describes the function of the sentence, as it asserts a direct, factual statement about the subject's actions.