As an aside on the stem in Arabic, I am amused to have seen the Almuwaḥidun—the Almohads, a dynasty of religious fundamentalist Muslims who conquered Spain and the Maghrib in the twelfth century—occasionally translated as "Unitarians", a religious group who couldn't be further apart from them. ("All of them believe in tea. Some of them also believe in biscuits.")
The Evil Doctor G | Homepage | 04.30.06 - 11:39 pm | #

More related words:

Ichud - Union
Yichud - Distinction
Chad- (prefix) - uni-

And the newest words to be related to echad, hot off the presses of the Hebrew Language Academy:

Yachda - Coalition (as in the ruling government)
Yachdani - Coalitional

(along with the counterpart Negda - Opposition)
Zman Biur | Homepage | 05.10.06 - 2:45 pm | #

See the Academy's decisions of 13 November 2005:
http://hebrew-academy.huji.ac.il.../ decision2.html
Zman Biur | Homepage | 05.10.06 - 3:03 pm | #