Youve probably heard of menopause , commonly known as the point at which a persons menstrual cycle stops for good. But it might surprise you that many symptoms that occur during menopause actually begin a lot earlier, during a phase called perimenopause.

Perimenopause refers to the time period when people start noticing inconsistency in their menstrual cycle, up until menopause actually begins. Menopause technically starts when someone has gone 12 months without a period. According to Nanette Santoro , chair of the Department of Obstetrics and Gynecology at the University of Colorado and a menopause researcher , the transition is marked by either a seven day or more increase in variability in your cycle length, or a skipped menstrual period.

This isnt to be confused with the word premenopause, which you may have heard tossed around before. That refers to the time up until a person starts experiencing menopausal symptoms (so basically now, if youre a person who gets a period), said Alyssa Dweck, author and New York-based gynecologist practicing for over 20 years.

Given that all the terminology, symptoms and timing can make an already confusing er, period, even more complicated, HuffPost chatted with experts on all things perimenopause to make it a little more clear. Heres what you should know about when it can happen, what to expect and how to alleviate any annoying issues:

When does perimenopause start?