I would think that it would be called the pen cap or the cap of a pen. Top of the pen or pen top may also be used. But I don't really believe that the lid of a pen is the correct use of the word "lid" in the phrase.
The part that covers the pen tip is called the cap or lid, while the top of the pen usually refers to the end opposite the writing tip where the cap is placed when not in use.
PenPencil
To keep the pressure equalized. If you have a pen with no hole, and were to take it up in an airplane, or even to the top of a building, the pressure difference could cause the ink to flow out of the pen creating a mess and making writing really messy. There is a hole in the body of the Compressed polystyrene to equalise atmospheric pressure, for the reasons stated above, however the hole in the top of the lid is to prevent children for sucking the lid into their throat, subsequently this provides an air passage in such a case.
The top of a box might be a lid. If there is no lid, there may be flaps.
it depends if you keep the lid on. it lasts longer if you keep the lid on. about 4 or 5 months.
pot top
The tip of the pen is the top because that's where you would put the pen cap
Remove 2 screws from the back holding the top lid, then slide the lid backwards and lift the lid.
the lid
On the lid of your Nintendo ds pen, there is a bit of string. On your ds (where you put you game card in), there will be 2 small squares. Put the string through one of them and it should come out of the other. Then open the string and put the lid through the gap then pull on the lid.
It means take the lid off the top of the cookpot.
lid
lid