other
In addition to the idioms beginning with other, also see at each other's throats; do unto others; each other; every other; in one ear and out the other; in someone's pocket (live in each other's pockets); in other words; laugh out of the other side of one's mouth; look the other way; made for (each other); none other than; on the one (the other) hand; or other; right (other) side of the tracks; shoe is on the other foot; six of one, half a dozen of the other; the other day; this and that (and the other); turn the other cheek; wait for the other shoe to drop.