A year ago, I asked my friend to pack his long johns on a trip to mountain skiing, and he was like, "What! I am taking my thermal underwear." And I was like okay! When we mate later that day, I told him that this is a long johns, but of course, he insisted it is "thermal underwear."

So, since that day, I have been trying to find Thermal underwear vs Long John's differences. First, I consider them different entities, but what really makes them different from one another?

I guess you are wondering too!

Thermal underwear vs Long johns
After doing my research and going through a dozen of online forums, I came to realize a few things. These things brought about people's perceptions of this two underwear, as well as what they deem to be the actual difference.

So, let's start and see what can find, right!

1.    PERCEPTION: According to most people, thermal underwear seems like a general term to them. But to some people, they see it as made from a specific fabric like

2.    HOW IT SOUNDS: The second point is that "to some long johns sounds colloquial and kinda funny," whereas "thermal pants" sound technically correct or serous if you may call it. But the fact is these two terms are interchangeable, meaning they relate in some ways.
Therefore, most Californians say that if you want to describe it perfectly or more accurately, then the ideal term to use will be "Thermal Underwear."

3.    MATERIAL: And now there is a group of people that differentiate the two using the type of material used. They say "Silk ones" are the long johns whereas the ones made with "waffly" sort of material are thermal underwear.

Which one are you? Or who do you think is right?

What I learned
Generally, there is no distinct difference between the two, even from the designers themselves. Therefore, they are all called thermal underwear. You could say thermal bottoms for the bottoms and thermal tops, or even thermal undershirt for the tops – to be specific.

However, some still say the term"long johns" only refers to the bottoms. And perhaps for the entire set of tops and bottoms, you can call it long underwear. So, is it true or just another perception?

Furthermore, "long johns" can be seen as an explicitly male garment, and since it refers to the bottoms, the tops will be thermal shirts. The other thing is the name "long johns" seems to be an outdated name, therefore, not frequently said by the under-40-year-olds.

For women, "long johns" remain as "long underwear," but for the long shirt, the word "shirt" may vary depending on how some may choose to call it. For example, "thermal Henley," which is another term that name that ladies can use to describe tops.

Final Thought
Overall, the names (thermal underwear and long johns) seems a bit like a generational thing. This is simply because the under 40 people barely say the name "long johns" instead, it seems to be famous among over-40-year-olds. But regardless of the name you choose, they all stand for one thing, but it's great to know more than one name, right?