length

• distance from end to end; period of time; extensiveness; section, piece (of fabric, etc.)
the length of something is the amount that it measures from one end to the other.
the length of a book, film, or speech is the amount of writing or material that is contained in it.
the length of an event, activity, or situation is the time it lasts.
the length of something is also its quality of being long.
in horse or boat racing, a length is the distance from the front to the back of the horse or boat, and is used as a unit of measurement..
a length of wood, string, cloth, or other material is a piece of it.
if something happens or exists along the length of something, it happens or exists for the whole way along it.
if you swim a length in a swimming pool, you swim from one end to the other.
if someone does something at length, they do it after a long time; a literary expression.
you can also use at length to refer to the fact that someone does something in great detail or for a long time; a formal expression.
if someone goes to great lengths to achieve something, they try very hard and perhaps do extreme things in order to achieve it.