For a pure wave motion in fluid dynamics, the Stokes drift velocity is the average velocity when following a specific fluid parcel as it travels with the fluid flow. For instance, a particle floating at the free surface of water waves, experiences a net Stokes drift velocity in the direction of wave propagation.

More generally, the Stokes drift velocity is the difference between the average Lagrangian flow velocity of a fluid parcel, and the average Eulerian flow velocity of the fluid at a fixed position. This nonlinear phenomenon is named after George Gabriel Stokes, who derived expressions for this drift in his 1847 study of water waves.

The Stokes drift is the difference in end positions, after a predefined amount of time (usually one wave period), as derived from a description in the Lagrangian and Eulerian coordinates. The end position in the Lagrangian description is obtained by following a specific fluid parcel during the time interval. The corresponding end position in the Eulerian description is obtained by integrating the flow velocity at a fixed position—equal to the initial position in the Lagrangian description—during the same time interval.
The Stokes drift velocity equals the Stokes drift divided by the considered time interval. Often, the Stokes drift velocity is loosely referred to as Stokes drift. Stokes drift may occur in all instances of oscillatory flow which are inhomogeneous in space. For instance in water waves, tides and atmospheric waves.

Peter Sheridan (born 1952) is an Irish playwright, screenwriter and director. He lives in the north side of Dublin.

His plays have a lyrical, vivid style amid tough dialog highlighting the difficulty and the promise of life in Ireland's capital. Awards include the Rooney Prize for Irish Literature. In 1980 he was writer-in-residence in the Abbey Theatre, Dublin, and his short film, The Breakfast, won several European awards. He wrote and directed the film Borstal Boy which was released in 2002.

He is the brother of the film director Jim Sheridan.

Sheridan, Peter (1999). 44, Dublin Made Me. New York: Viking. ISBN 0-670-88514-2. 

Sheridan, Peter (2004). Every Inch of Her. New York: Penguin Books. ISBN 0-14-200434-0. 

Sheridan, Peter (2003). 47 Roses. New York: Penguin Books. ISBN 0-14-200286-0. 

"IMDB". http://www.imdb.com/name/nm0792241/. Retrieved 2007-06-05. 

"Irish Playography". http://www.irishplayography.com/search/person.asp?PersonID=3788. Retrieved 2007-06-05.