comprise and compose - the difference
 
Comprise means to consist of (e.g., The cake comprises four slices.) Some quirks:

(1) No of with comprise (e.g., It comprises of... ).
(2) Avoid the construction is comprised of.
(3) Avoid naming the constituent parts first (e.g., Four slices comprise the cake.)

Compose means to make up (e.g., Four slices compose the cake.)
 


There is often confusion over comprise and compose. The situation is not helped by ongoing debate about how to use comprise. If you stick to the guidelines below, you will be on safe ground.

Comprise

To comprise means to consist of or to be made up of. It is used to denote that something is made up of smaller parts. Do not use the word of with comprise.

Examples:

The water molecule comprises two atoms of hydrogen and one atom of
oxygen.
(The whole comprises the smaller parts.)

The water molecule comprises of two atoms of hydrogen and one atom of
oxygen.
(Do not use the word of with comprise.)

Two atoms of hydrogen and one atom of oxygen comprise the water molecule.
(This is one of the areas under debate. Many advocate that comprise cannot be used to denote that the smaller parts make up the whole. They believe this is when compose should be used. If you adhere to this ruling too, you will never be wrong.)

The three wise monkeys comprise Mizaru (see no evil), Kikazaru (hear no evil) and Iwazaru (speak no evil).
 
The quadriceps femoris comprise the rectus femoris, the vastus medialis, the vastus intermedius and the vastus lateralis.

Is Comprised Of

The construction is comprised of (note: it correctly includes the word of) is considered by many to be non-standard English. To avoid criticism, reword your sentence to avoid this construction.

Examples:

The water molecule is comprised of two atoms of hydrogen and one atom of oxygen.
(Contentious version. Some of your readers may frown at this version.)

The water molecule comprises two atoms of hydrogen and one atom of
oxygen.
(Reworded, non-contentious version)

Compose

To compose means to make up or to make. It is used to denote that parts make up the whole (i.e., the opposite of comprise). Do not use the word of with compose.

Examples:

Mercury, Venus, Earth and Mars compose the inner planets.

The rectus femoris, the vastus medialis, the vastus intermedius and the vastus lateralis compose the quadriceps femoris.

Two atoms of hydrogen and one atom of oxygen compose the water molecule.

Is Composed Of

The construction is composed of (note: it correctly includes the word of) does not attract the same criticism as is comprised of

Examples:

USA is composed of 50 states.

The water molecule is composed of two atoms of hydrogen and one atom of oxygen.
 
Select the correct version:



 
 

 
NAME ALL THE CONSTITUENT PARTS

Make sure you name all the constituent parts when using comprise or compose.

Since August 2006 when the International Astronomical Union declassified Pluto as a planet, only eight planets compose our solar system.

(Our solar system also includes the Sun, an asteroid belt and a number of dwarf planets.  Therefore, compose is incorrect in this example.)

BEWARE INCLUDE

Do not name all the constituent parts when using include.

The water molecule includes two atoms of hydrogen and one atom of oxygen.
The water molecule includes one atom of oxygen.
 

See also:

Common errors and FAQs
List of easily confused words