Is theta always negative?

Could you please clarify for me, is theta always a negative value? I've been reading about it in relation to financial markets and cryptocurrencies, but the information seems contradictory. Some sources suggest that theta can indeed be negative, while others indicate that it can also take positive values. I'm trying to understand the conditions under which theta would be negative and when it might be positive. Could you explain this further? Additionally, how does theta's value affect market movements and cryptocurrency prices? I'm particularly interested in understanding its role in risk assessment and hedging strategies. Thank you for your assistance in clarifying this topic for me.