Graph paper, graphing paper, grid paper or millimeter paper is writing paper

Paper

Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....

 that is printed with fine lines making up a regular grid

Regular grid

A regular grid is a tessellation of n-dimensional Euclidean space by congruent parallelotopes . Grids of this type appear on graph paper and may be used in finite element analysis as well as finite volume methods and finite difference methods...

. The lines are often used as guides for plotting mathematical functions or experimental data

Experimental data

Experimental data in science is data produced by a measurement, test method, experimental design or quasi-experimental design. In clinical research any data produced as a result of clinical trial...

 and drawing diagram

Diagram

A diagram is a two-dimensional geometric symbolic representation of information according to some visualization technique. Sometimes, the technique uses a three-dimensional visualization which is then projected onto the two-dimensional surface...

s. It is commonly found in mathematics and engineering education settings and in laboratory notebooks. Graph paper is available either as loose leaf

Loose leaf

The term loose leaf is used in the United States, Canada, and some other countries to describe a piece of notebook paper which is not actually fixed in a spiral notebook...

 paper or bound in notebook

Notebook

A notebook is a book or binder composed of pages of notes, often ruled, made out of paper, used for purposes including recording notes or memoranda, writing, drawing, and scrapbooking....

s.