Imagine a big circle around the Earth, like a hula hoop. This circle is divided into 360 smaller parts, each one called a degree. These degrees help people find places on Earth more easily.
The 109th meridian west is one of those degrees. It is an imaginary line that runs from the North Pole to the South Pole, passing through North America and the Pacific Ocean.
Now, let's pretend you are standing right on the 109th meridian west line. If you move to the east, you will start going towards the 108th meridian west. If you move to the west, you will be heading towards the 110th meridian west.
But what's really important about the 109th meridian west is that it is used as a time zone boundary in North America. This means that the time in places to the east of this line is different from the time in places to the west of it.
So if you were on the 109th meridian west line in North America, and you walked to the east, you would be going into a time zone where the time is one hour earlier than on the line. And if you walk to the west, you'll be entering a time zone where the time is one hour later than on the line.
That's because the 109th meridian west acts as a boundary between two different time zones: Mountain Time Zone to the east and Pacific Time Zone to the west.
So, the next time you hear someone talking about the 109th meridian west, you'll know it's an imaginary line that helps us find our way on Earth and tells us what time it is in different parts of North America.