monochromatic: containing or using only one color.

Source : Google.com 

My definition : involves the use of one color

Example : 

Analogous Colors: Analogous color schemes often mimic the color schemes found in our natural environment and can create a calm and relaxed feel when applied in design.

Source : http://graf1x.com/definition-of-complementary-analogous-triadic-and-split-complementary-color-schemes/

My definition : Analogous colors are colors that utilize  up to 3  or more colors that are complements, and are adjacent to each other.

Example : 

Triad : The Triadic color scheme is aptly named as it consists of three colors that are spaced evenly around the color wheel; when the colors are linked by a straight line, they form a triangle.

Source : http://graf1x.com/definition-of-complementary-analogous-triadic-and-split-complementary-color-schemes/

My definition: a color scheme that utilizes colors that are lined up to create the shape of a triangle.

Example : 

Tetrad: A color scheme arrangement derived from the color wheel that contains four colors.

Source : http://www.creativeglossary.com/color/tetrad.html

My definition:any four colours which are equidistant on the colour wheel that form a rectangle shape.

Example :