Final answer:
The term 4. 'recurrence' refers to the time between same-sized natural disasters and is used as a statistical measure to express the likelihood of such events occurring within a given timeframe.
Step-by-step explanation:
The term for the amount of time between same-sized natural disasters is 4. recurrence. This term is often used in the context of natural events such as floods, where a 'recurrence interval' is used to indicate the probability of a flood of a certain magnitude happening within a given year.
For example, a '3-year flood' is one that has a 1-in-3 chance of occurring each year. This does not guarantee that floods will occur at exact intervals, similar to how rolling a dice does not ensure that a 4 will appear every sixth roll.
Instead, the recurrence interval is a statistical measure used to gauge the likelihood of such events and is a crucial concept in disciplines like environmental science and geography.