A fin is a surface used for stability and/or to produce lift and thrust or to steer while traveling in water, air, or other fluid media, (in other words, a foil (fluid mechanics)). The first use of the word was for the limbs of fish, but has been extended to include other animal limbs and man-made devices. Fins, as with other foils, operate in fluids such as water or air.

Fins are seen both in nature and in manmade iterations.

Swimming water animals such as fish and cetaceans actively use pectoral fins for maneuvering, and dorsal fins contribute stability as the animal swims, propelling and maneuvering with its tail, itself recognizable as a fin.

The fin on fixed-wing aircraft is known as a vertical stabilizer. Fins are also seen used as e.g., fletching on arrows and at the rear of some bombs, missiles, rockets, and self-propelled torpedoes. These are typically "planar" (shaped like small wings), although grid fins are sometimes used in specialized cases.

Examples of fins include:

In surfing, there are two major types of (typically stationary) surfboard fins (hydrofoils), and a host of illustrative issues.

In vector calculus, del is a vector differential operator, usually represented by the nabla symbol ∇. When applied to a function defined on a one-dimensional domain, it denotes its standard derivative as defined in calculus. When applied to a field (a function defined on a multi-dimensional domain), del may denote the gradient (locally steepest slope) of a scalar field, the divergence of a vector field, or the curl (rotation) of a vector field, depending on the way it is applied.

Strictly speaking, del is not a specific operator, but rather a convenient mathematical notation for those three operators, that makes many equations easier to write and remember. The del symbol can be interpreted as a vector of partial derivative operators, and its three possible meanings—gradient, divergence, and curl—can be formally viewed as the product of scalars, dot product, and cross product, respectively, of the del "operator" with the field. These formal products do not necessarily commute with other operators or products.

Mundo may refer to:

Jennifer Marcella Peña (born September 17, 1983 in San Antonio, Texas), is an American Latin Pop/Tejano singer and actress who has sold over 3.5 million records internationally. Peña is the third and youngest daughter of Jaime and Mary Peña with other siblings Janet and Jackie. Peña is of Mexican descent native to the state of Texas raised in Corpus Christi, Texas.

Peña first achieved notoriety after performing at the Astrodome in Houston, Texas during a Selena tribute concert in 1995 while under management with Q Productions and Abraham Quintanilla II, who was Selena's father and former manager. This was Peña's first public performance on a grand scale performing Bidi Bidi Bom Bom, a #1 song for the late Latin superstar Selena. Peña's first studio album Dulzura released in May 1996 as part of Jennifer y Los Jetz was produced by Abraham Quintanilla III and introduced her to the music scene officially at the age of 12 with the title track and "Ven a mí" (a Spanish-language cover of The Drifters' "Dance with Me") garnered her a loyal fanbase. The album sold quite well in the Latin market, certified gold and winning several Tejano Music Awards. At the time Tejano Music was in its prime and Jennifer was another staple act in the scene. Her introduction was both praised and criticized mainly in part due the artistic similarities between Selena and she. The comparisons came and went, but Jennifer managed to continue winning over fans. The year 1997 saw the release of her second album, Jennifer Y Los Jetz , with the singles "Tu Castigo" and "Yo Te Vi", being promoted and drawing the same level of success Dulzura had achieved winning another gold certification.

Maricarmen Marín is a Peruvian actress, cumbia singer and dancer, and television program host. She started as a dancer in the musical show "La movida de los Sabados" and she became famous as the lead singer of the female technocumbia musical group "Agua Bella". Maricarmen participated in El Gran Show in 2010. In 2011 she currently stars as Natasha in the America Television series "Yo no me llamo Natacha" (English: "My name is not Natacha") for which she also performed the theme song. She is also currently a solo singer.