Supporting Details

A very important reading skill one can acquire is finding the main idea in a passage or reading. A closely related reading skill is locating supporting details. Supporting details are reasons, examples, facts, steps, or other kinds of evidence that back up and explain a main idea. 


Details make up most of the information in what a person reads, but some details are more important than others. There are two kinds of supporting details: major and minor. Just as the main idea is the most important idea and more general than its supporting details, major details are the most important and are more general than the minor details. The minor details are more specific and help fill out and explain the major details.


Major details are important to comprehension which is increased when one asks which of the details are most important and why. Primary purposes of major details are listed below with brief explanations:

Identifying Major Supporting Details


Preparing an outline of a passage often helps one understand and see clearly the relationship between a main idea and its supporting details. Outlines start with a main idea followed by the major supporting details and then the minor details. The template of an outline looks like the following:

Main Idea

Below is an example of an outline from a passage dealing with factors interfering with memory.

Main idea: Several factors can interfere with having a good memory.

The major details in the above outline serve as reasons why we may have difficulties with remembering information. The minor details are more specific and explain in detail the major supporting details.

Signal Words

Another tip to identifying major supporting details is to look for words that signal major details. Here are some common signal words:


to begin with



first (of all)

for one thing

in addition





last (of all)






In the selection below each of the bold signal words indicate or announce a major detail being explained. The main idea in this case is the first sentence.

Although only human beings communicate through words, other animals also communicate in their own ways. First, animals can communicate by means of nonverbal sounds, such as chirps and birdsong, mews, barks, howls, and roars. Next, animals communicate through chemical signals: male dogs, for instance, use urine to mark their own turf. A third means of animal communication is touch, such as nuzzling and licking—as well as grooming among, for example, monkeys. Last of all, animals communicate by visual signals. Dogs, of course, wag their tails; also, they and some other furry animals raise their hackles (the hairs between the shoulders) when threatened, in order to appear larger. Baring the teeth is another visual signal. And honeybees perform a famous "wiggle dance" to inform each other about sources of food.


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Practice 1

Practice 2