You walk into Macy's. You head to the Dockers Department. You start browsing. These All Weather Alpha 360 Flex Slim Tapered Fit Chinos look nice! Ok, I'll grab 36x34 and also 38x34. But wait? Mixed in with these pants are a pair that are labeled slightly different, with a different sticker signifying the size. They seem pretty similar. But wait. These are Alpha 360 Flex Slim Tapered Fit KHAKIS. Ok sure I'll grab some of these, too!
Soon you're in a dressing room. First, the CHINOS. Ok, the 36" waist feel a bit too snug, and the 38" feels a bit too big. Both pretty good, but perhaps I should lose a little wait to fit perfectly into the 36's, or gain a little for the 38's? Or perhaps I need skinny summer pants and fat winter pants? But wait! Right now, I only wearing a polo shirt while trying on these pants. Often, I would be wearing a dress shirt and undershirt. So with the two layers, perhaps the 38's will fit well? Ok, but what about the khakis? Ok, these seem slightly THINNER, but they seem tighter!
You head back out to the racks. Oh, there is also STRAIGHT fit. Perhaps a 36" waist in the straight will be good, because it's a fuller cut? But actually, the waist is the same, it's really just the cut of the leg that is fuller, and you have relatively slim legs.