Probably primary fermentation is complete. Leave it for another week.
It could also be things like fermentation has slowed, because the ambient temperature has dropped, and it is not complete. Or a whole bunch of other reasons.
One of the easiest ways to get a better idea of what is going on in the ferment is to take a sample, and test it with a hydrometer. Generally the idea is to test it before adding yeast, and when you think fermentation is complete. Of course, it can be tested in-between too.
The hydrometer measures the density of a liquid, and suspended sugar increases the density. When the yeast converts the sugar into ethanol, the density decreases. So by taking measurements, it becomes clear just how much sugar remains in the ferment. These measurements will also allow you to calculate how much alcohol is in your final beverage. So it's worthwhile to buy the (inexpensive) equipment, and take the time to test.
Generally you can tell the fermentation is complete when the hydrometer reading is approximately where you expect it to finish, and there has been no further changes for 3 days. I write "generally", because environmental factors need to be taken into account too - if there's been no change for 3 days, but your fermenter has frozen solid, well that's a different matter.
So assuming you don't have this gear, what can you do. First, I would wait until at least two weeks are past. At the end of fermentation, the yeast will start to settle to the bottom. So if the fermentation vessel is clear, you can watch for this. There should be absolutely no issues leaving the ferment for 2, or even 3 weeks on the yeast. If it's cool/cold, even longer.
You can also taste the mead, if it's still really sweet, generally fermentation isn't finished. (This assumes there wasn't so much sugar, that the yeast can process it entirely).
Note that it's important to leave the yeast to finalise the fermentation. During the initial vigorous phase of fermentation, the yeast makes some untasty by-products. But once the first phase is done, the yeast re-processes these compounds into something else (that doesn't taste bad). If you package or quickly refrigerate the ferment before this happens, the quality of your final beverage will suffer.