Final answer:
Anxiety is characterized as nervousness or agitation about something that is going to happen, especially in relation to stress and the fight-or-flight response. An anxiety disorder involves long-lasting and intense feelings of worry that disrupt daily life.
Step-by-step explanation:
Anxiety is indeed characterized as nervousness or agitation about something that is going to happen. This feeling of worry or fearfulness can be a normal reaction to stress, which happens in response to our surroundings. Stress can manifest physically by an increased heart rate, rapid breathing, and tensing of muscles, as part of the fight-or-flight response. While this response was crucial for survival in our ancestors' time when dealing with physical threats, in the modern world, these responses to psychological threats can lead to negative health consequences if they persist for long periods. An anxiety disorder is when these feelings of anxiety are intense and long lasting, affecting a person's day-to-day life and wellbeing.