|This article relies largely or entirely upon a single source. (October 2013)|
Ioci is a Latin term and is loosely translated as "joke or humor." Cicero speaks of ioci in his theory of humor and uses ioci as a general term that encompasses much about the effective use of humor and jokes for orators.
Ioci in "De Oratore"
In Cicero's De Oratore, he defines ioci through a discussion between Julius Caesar and Antonius. Caesar is the primary speaker and is responding to a request from Antonius for him to explain "wit" since the group agrees he commands a mastery of the art; which can not necessarily be taught but is instead something learned naturally. Caesar enlightens them to two types of wit: Humor and Jesting. He explains that humor is something that can be sustained throughout a speech's entirety, and is more favorable, while a jest is something "pointed and concise," much like a joke. 
Antonius surmises that Caesar is saying that jokes should be suppressed when there is no need for them and asks when and how they can be used. He points out that a joke is impressive and shows quick wit, adding that they can be better objections than a broken argument.
Caesar responds by stating that there are five dimensions of laughter.
- What it is (simply what laughter is in itself).
- Whence it originates (to point out something offensive in an inoffensive manner).
- Whether it becomes the orator to wish to excite laughter (to attract favour; such as hampering an adversary or refuting him. This also breaks the force of offensive remarks).
- To what degree (gauging the situation and deeming appropriateness).
- What are the several kinds of the ridiculous (the humor must be in good taste so that the orator doesn't fall victim to buffoonery or mimicry).
Other notes about ioci include that an orator should not simply aim to raise a laugh, but it should be part of their argument. Pointless joking will lead to buffoonery. Caesar gives warning that not all that is ridiculous is witty. He also mentions that the most common joke is when we expect one thing but instead another is said, leading us to laugh at our own disappointment.
Cicero's De Oratore Book II 217-255 Pomona College. Retrieved 2013-10-21