General indifference:
* Apathetic: Lacking interest, enthusiasm, or concern. (Stronger than indifferent)
* Uninterested: Not interested or concerned. (Similar to indifferent, but more focused on lack of interest)
* Unconcerned: Not worried or bothered. (Emphasizes lack of worry)
* Detached: Emotionally distant or uninvolved. (Implies a feeling of separation)
* Impassive: Showing no emotion or reaction. (More about lack of outward expression)
Specific types of indifference:
* Ambivalent: Having mixed feelings or contradictory ideas about something. (Indifferent to both good and bad aspects)
* Neutral: Not favoring one side or another. (More about neutrality)
* Unbiased: Not influenced by personal opinions or feelings. (Emphasizes fairness)
* Cold: Lacking warmth or feeling. (More about coldness)
* Aloof: Distant and uninterested in others. (More about social detachment)
Informal:
* Don't care: A casual and direct way to say you're indifferent.
* Couldn't care less: Expresses extreme indifference.
The best word to use will depend on the context and the specific shade of meaning you want to convey.