Last night as I went to sleep, a thought popped in my head: "Shoot, when I did laundry, I forgot to wash my pillow sack! ... Uh, did I just say pillow sack??" It then occurred to me that at that moment, for some reason, the first descriptor for the cloth sheath that enveloped my pillow was strangely pillow sack and not pillowcase. I pondered that for a while and couldn't figure out why I had referred to it as that. I could also not remember what I grew up calling it (other than 枕頭袋), or whether pillow sack and pillowcase even refer to the same sort of object. I must have been so perplexed as I fell asleep that this deliberation resurfaced among my first thoughts this morning. (It came second only to Seeing that I was just awoken by thunder in the middle of winter, does that mean it's raining or snowing? A coworker told me that it was a thundersnowstorm.) I eagerly climbed out of bed and rushed to my computer to google "pillow sack". I couldn't find a definition anywhere and text including the term assumed the reader already knew what a pillow sack is. Google Images tells me that pillow sacks apparently range from tight-fitting covers for cushions to huge cloth bags. I've thought about it on and off the rest of today and I'm still no closer to reconciling the two terms, lacking evidence to differentiate or equate. So as I prepare for bed tonight, I'm still confused. Apparently, it doesn't take very much to confuse me nowadays...