schizō

At its heart this word describes one action: a whole thing pulled or broken into pieces so that it is no longer one. The pieces can be soft, like a torn garment or a ripped curtain or net, or they can be solid, like split rock or the opened sky. English needs two different words for this, tear for cloth and split for stone, but the Greek uses a single word for both.

What ties these uses together is the sense of a clean, decisive break, not a small tear you could stitch back up. The Greek Old Testament used this same word for splitting firewood, for the Red Sea parting, for rock broken open in the desert, and for the mountain that will be split in two on the day of the Lord. That background gives the word a heavy feel. When one Gospel says the sky was torn open as Jesus came up from the water, it pictures the heavens broken like something solid, not gently parted.

The Gospel writers return to this word at their most charged moments: the sky at the baptism, the temple curtain torn from top to bottom at the crucifixion, the rocks split as Jesus dies. John turns it the other way, twice pointing to something that is deliberately not torn: the seamless robe the soldiers would not rip, and the full net that did not tear.

This is the same picture of tearing, now applied to a group of people instead of an object. When a crowd or a council breaks into opposing sides over something, the Greek describes it as being torn in two, the way a piece of cloth is torn.

Greek writers used the word this way long before the New Testament, for an army divided or opinions split down the middle, so this is an ordinary extension of the word rather than a fresh coinage. In Acts it describes first a town and then a ruling council breaking into two camps over a question they cannot agree on.