# 'Bilogy'? What is a two-member set? **URL:** \ **Category:** Factual Questions\ **Created:** [February 25, 2005, 4:57pm UTC](https://boards.straightdope.com/t/bilogy-what-is-a-two-member-set/291898 "2005-02-25T16:57:41Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [February 25, 2005, 4:57pm UTC](https://boards.straightdope.com/t/bilogy-what-is-a-two-member-set/291898/1 "2005-02-25T16:57:41Z")
While watching _Alien[sup]3[/sup]_ last night, I thought about how ‘quadrilogy’ isn’t a word. A set of four dramatic or literary works is a tetralogy. A three-member set is a trilogy. But what’s a two-member set? ‘Bilogy’ isn’t a word. Also, it’s pretty useless to have a word for a single film. In writing, it’s called a monograph. Is there a word for a single film? ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [February 25, 2005, 5:32pm UTC](https://boards.straightdope.com/t/bilogy-what-is-a-two-member-set/291898/2 "2005-02-25T17:32:24Z")
> [@Johnny L.A.](#): > > While watching _Alien[sup]3[/sup]_ last night, I thought about how ‘quadrilogy’ isn’t a word. A set of four dramatic or literary works is a tetralogy. A three-member set is a trilogy. But what’s a two-member set? ‘Bilogy’ isn’t a word. > > Also, it’s pretty useless to have a word for a single film. In writing, it’s called a monograph. Is there a word for a single film? Well, since we’re looking at Greek and not Latin roots, the word would be something like “duology.” A quick Google search of “duology trilogy quadralogy” seems to indicate it does exist, albeit rare. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [February 25, 2005, 5:38pm UTC](https://boards.straightdope.com/t/bilogy-what-is-a-two-member-set/291898/3 "2005-02-25T17:38:14Z")
> [@pulykamell](#): > > Well, since we’re looking at Greek and not Latin roots, the word would be something like “duology.” A quick Google search of “duology trilogy quadralogy” seems to indicate it does exist, albeit rare. [Dictionary.com](http://Dictionary.com) does not have an entry for ‘duology’, ‘quadrilogy’ (as it’s spelled on the DVD box), or ‘quadralogy’. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [February 25, 2005, 5:41pm UTC](https://boards.straightdope.com/t/bilogy-what-is-a-two-member-set/291898/4 "2005-02-25T17:41:50Z")
> [@Johnny L.A.](#): > > [Dictionary.com](http://Dictionary.com) does not have an entry for ‘duology’, ‘quadrilogy’ (as it’s spelled on the DVD box), or ‘quadralogy’. :smack: I meant “tetralogy,” of course. “Quad” is Latin. “Tetra-” is Greek. ---
**Author:** ![phouka](https://avatars.discourse-cdn.com/v4/letter/p/c5a1d2/32.png) [@phouka](https://boards.straightdope.com/u/phouka)\ **Post date:** [February 25, 2005, 6:30pm UTC](https://boards.straightdope.com/t/bilogy-what-is-a-two-member-set/291898/5 "2005-02-25T18:30:59Z")
In the art world, a two part piece is referred to as a diptych, and a three part piece is a triptych. Hope that helps. ---
**Author:** ![Inigo\_Montoya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inigo_montoya/32/124_2.png) [@Inigo\_Montoya](https://boards.straightdope.com/u/Inigo_Montoya)\ **Post date:** [February 25, 2005, 7:58pm UTC](https://boards.straightdope.com/t/bilogy-what-is-a-two-member-set/291898/6 "2005-02-25T19:58:33Z")
I’m such a gutter dweller. I thought the answer was “Hemi Penis” ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 25, 2005, 10:27pm UTC](https://boards.straightdope.com/t/bilogy-what-is-a-two-member-set/291898/7 "2005-02-25T22:27:09Z")
> [@](#): > > Also, it’s pretty useless to have a word for a single film. In writing, it’s called a monograph. Is there a word for a single film? I was under the impression that a monograph is a piece of writing (generally a scholarly paper) written by a single author, not one for which there was no sequel. ---
**Author:** ![Orbifold](https://avatars.discourse-cdn.com/v4/letter/o/779978/32.png) [@Orbifold](https://boards.straightdope.com/u/Orbifold)\ **Post date:** [February 25, 2005, 10:35pm UTC](https://boards.straightdope.com/t/bilogy-what-is-a-two-member-set/291898/8 "2005-02-25T22:35:21Z")
The [last time](http://boards.straightdope.com/sdmb/showthread.php?t=249203) we hashed this out, I think we settled on “duology”.