Hmm, this is a succulent-looking word, don’t you think? A little lexical Lucullan delight? Or perhaps a sultry seducing succubus? Are you doing a mental calculus on how it inculcates its sense? Are you furrowing your brow? Do you dig this word, is it groovy?
It is a groove, that much is true. A furrow. A wrinkle. A trench. An involution, a mark of graving. That’s what it signifies in Latin, and it has come to English with the same general sense, but it has fit itself into more specific niches. It is a groove made with an engraving tool. Or a rut, or a fold in the landscape. Or it is a groove or furrow somewhere on or in the body. But especially it is a groove in the brain.
Your brain, as you probably know, is as wrinkled as a shar-pei’s face. Your cerebral cortex (that’s Latin for ‘brain bark’) has a lot more area than your skull does, so it just folds in and out like a T-shirt stuffed in a can. The parts that are folded out so you can see them if you’re holding a brain are called gyri (singular gyrus), and the parts that are folded in are called sulci (plural of sulcus, obviously). The brain also has a few deeper splits between parts; these are called fissures.
That plural, sulci. Think for a moment about how you would pronounce it. If you think about it from the pronunciation first, you may come up with “sulk eye.” If you start with the spelling, you may prefer “sull sigh.” Or you may get sulky.
I mean “sulky,” another possible pronunciation. All are attested, and all are acceptable (though the older English style is “sull sigh” and the original Latin is closer to “sulky” – actually more like “sool key”). You should decide which you like best, because sulci often come in groups.
Or you could just stick with the little ones. A little sulcus is a sulculus, and if that isn’t succulent I don’t know what is. And its plural is sulculi, so at least you don’t have to worry about that “k” versus “s” thing. But if you do worry about it, you have your sulci – and gyri – to thank for it.