It's listed in the new PHB, but there's no description.
It's a mundane real world tool used for calculation. You should be able to google an image pretty easily.
Dastion wrote:
Technically, an abacus does nothing. A PC does things with an abacus. Most people might recommend using it for math, but the occasional weapon attack works for me. I'll attack with a bowl of salad if it comes down to it. An abacus is an upgrade from there. 
What does an abacus do? Depend on your class:
Barbarian: It breaks easy.
Bard: It makes a cool rattling sound when shaken.
Cleric: It tallies your tithes.
Fighter: 1d3 damage as an improvised weapon.
Monk: It keeps your chants in order.
Ranger: Add some string and make a tripwire alarm.
Rogue: The greatest crimes of all
Sorcerer: Burns easily.
Warlock: Tallies your debt to Baalzebub
Wizard: Unlocks the secrets of the universe!
Luke-Lightning wrote:
Paladin of Vengeance, dedicated to Waukeen, needs one to know exactly how much debt to beat out of you; with reasonable interest and penalties for late payment of course.
On a more serious note, Im surprised it wasn't rolled into 'Merchant's Tools' with weights and scales; a tool I noticed as absent from the list in the PHB.
I am kind of surprised there are people unaware of an abaci's function. I thought it was something that all students are exposed to in elementary school? At least it was some 20+ years ago when I was said elementary student. I recall using one as early as grade 2, alongside the use of those wooden counting blocks.
trentthefox wrote:
GreyMorgan wrote:
It will also occupy toddlers for a little while.
Kalani wrote:
It allows you to be able to relive the memories of your ancestors.
Ah, this discussion really makes me remenisce about my first days of playing D&D. I learned so many new words. Cleric. Battlement. Keep. Castellan. Homlet. Chaotic. D&D was my first exposure to so many words!
Kalani wrote:
Kalani wrote:
You can use the abacus to calculate the number of days that have passed since this thread was last under discussion, for example.
SpedGuy wrote:
Luke-Lightning wrote:
iserith wrote:
trentthefox wrote:
I still giggle knowingly when someone uses the word "Streetwise"
An abacus is an improvised weapon that does 1d4 points of damage on a hit.
Ganymede425 wrote:
One could also say that an abacus is a non-magical variant of the Abacus of Calculation (published in Dragon 73, and presumably acceptable in 5e since its abilities don't really impinge on game mechanics, much like the non-magical abacus):
Abacus of Calculation
This device is a simple wooden frame, about 8 by 10 inches. Several heavy wires are strung across the frame, parallel to one another. On each wire are 10 wooden balis. When mathematical formulas involving numbers (adding, subtracting, multipingly, dividing and simple operations) are spoken near the object, the balls shift about and the answer is spoken aloud by a disembodied voice.
Now, what use is an Abacus of Calculation? I think actually that items like that would be far more useful than magic swords and armor -- not to adventurers, but most people aren't adventurers. I would think that in any civilized world that had magic items, things like this would be more common than the stuff that adventurers typically seem to find. Of course, as useful as this item might be to certain merchants, if it exists, there has to be a version of that will selectively make certain mistakes when dealing business with certain individuals. Watch out for the long con.