Final answer:
A stressor is an event or situation that causes stress.
Step-by-step explanation:
A event or situation that causes stress is called a stressor. Stressors can be events or situations that are demanding or threatening, such as a high-stress job or final exams week. They can also be chronic stressors that persist over a long period of time, like caring for a parent with dementia or long-term unemployment. The word that best completes the sentence in the space provided, referring to an event or situation that causes stress, is called a stressor. This term accurately captures the essence of environmental events or stimuli that initiate the stress process, potentially leading to the experience of stress when these events are judged as threatening or demanding. The complexity of how stress is defined and understood in various contexts, such as physiology, job satisfaction, and personal well-being, is also highlighted in the provided reference information. Stressors can be chronic, such as long-term unemployment; acute, like a physical injury; or even environmental pressures that challenge one's ability to cope.