ad libitum

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Look up ad libitum in Wiktionary, the free dictionary.

Ad libitum is Latin for "at [one's] pleasure"; it is often shortened to "ad lib" (as an adjective or adverb) or "ad-lib" (as a verb or noun). The roughly synonymous phrase a bene placito ("at [one's] good pleasure") is less common but, in its Italian form a piacere, entered the musical lingua franca (see below).

Music

As a direction in sheet music, ad libitum indicates that the performer or conductor has one of a variety of types of discretion with respect to a given passage:

• to play the passage in free time rather than in strict or "metronomic" tempo (a practice known as rubato when not expressly indicated by the composer);
• to improvise a melodic line fitting the general structure prescribed by the passage's written notes or chords;
• to omit an instrument part, such as a nonessential accompaniment, for the duration of the passage; or
• in the phrase "repeat ad libitum," to play the passage an arbitrary number of times (cf. vamp).

Note that the direction a piacere (see above) has a more restricted meaning, generally referring to only the first two types of discretion.

Biology

Ad libitum is also used in psychology and biology to refer to the "free-feeding" weight of an animal, as opposed, for example, to the weight after a restricted diet. For example, "The rat's ad libitum weight was about 320 grams." In nutritional studies, this phrase denotes providing an animal free access to feed or water thereby allowing the animal to self-regulate intake according to its biological needs. For example, "Rats were given ad libitum access to food and water."

In biological field studies it can also mean that information or data were obtained spontaneously without a specific method.

Medical prescriptions may use the abbreviation ad lib. to indicate "freely" or that as much as one desires should be used.

Drama

In action, the quick-witted invention of dialogue to cover a performer's memory lapse would be described as an ad-lib. Or, a director might encourage performers to ad-lib in a particular show. The term ad-lib usually refers to the interpolation of unscripted material in an otherwise scripted performance. When the entire performance is predicated on spontaneous creation, the process is usually called improvisation, such as in the show Whose Line Is It Anyway?

Live performers such as television talk-show hosts (e.g., Jay Leno, David Letterman, etc.) sometimes enhance their reputation for wit by the delivery of material that sounds ad-libbed but is actually scripted, and may employ ad-lib writers to prepare such material. Some actors are also known for their ability or tendency to ad-lib, such as Peter Falk (of the series Columbo), who would ad-lib such mannerisms as absent-mindedness while in character.

It is a common misconception^{[citation needed]} that "ad lib" stands for "adding liberally". Although it may hold the same meaning, the origin is not true.

See also

• List of Latin phrases
• Ad infinitum
• Ad nauseam