Harlem Summary

Get out the microscope, because we’re going through this poem line-by-line.

What happens to a dream deferred?

If we were to answer this question right away, we'd probably say, "Nothing much, Mr. Speaker, it will probably just fade away."
But there's something about the way our speaker says "dream deferred" instead of "deferred dream" that makes us realize that we are not in the world of logical rationale, but rather the far cooler world of poetry, truth telling, and soul-searching. By beginning this poem with a question, we readers are put on the spot.

Does it dry up

What happens when things dry up? Well, they lose their moisture and their water. They become small and withered. This line makes us think of deserts and summers and heat.
Notice each of the words in this line only contain one syllable.

like a raisin in the sun?

Raisins are supposed to be dry, right? They become raisins by sitting in the sun. Well, actually, raisins begin as grapes and gradually lose their juice when they are put out in the sun. Raisins are totally delish and tasty, but they're not quite as succulent as grapes, in our humble opinion.
[We interrupt this program to alert you to a Really Cool Literary Fact (an RCLF). Famous American playwright Lorraine Hansberry took the phrase "a raisin in the sun" as the title of her play, A Raisin in the Sun. This play quickly became one of the most beloved works in American theater as it captures the deferred dreams of a black family living in Chicago during the 1950s.]

Or fester like a sore—

Eww, "fester." Whenever we hear that word, we can't help but think of an open wound full of puss and blood.
Usually, things fester when they aren't healing or when they aren't being cared for properly. Here, our speaker suggests a deferred dream won't heal or go away.

And then run?

We know our speaker is continuing with the wound image here, wondering if dreams bleed themselves to death if they are ignored.
However, there's something very powerful about the word, "run." We can't help but think about other meanings for it, meanings like "escape" or "flow."

Does it stink like rotten meat?

If dreams are stashed away, will they haunt us like rotten meat haunts us when it sits too long in the refrigerator? If rotting meat didn't smell so bad, how much longer do you think it would sit in your fridge? The smell is often what reminds us to do something about it, to throw it away.
This line stirs our sense of smell, because most of us have had an experience with the smell of rotten meat before. This is a smell closely associated with death.
In this line, our speaker makes an interesting distinction between ignoring dreams and getting rid of them altogether. We are reminded that "a dream deferred" is an ignored dream, not a canceled dream.

Or crust and sugar over –

What kinds of things crust or sugar over? Honey. Cheese. Candy. Usually things that left out in the open and that aren't put away properly.
Can dreams be put away properly? Can dreams be preserved if they aren't pursued?
Our speaker compares dreams to sweet-tasting things, stirring our taste buds and drawing a contrast to the bitterness of lost dreams.

like a syrupy sweet?

Syrup reminds us of pancakes and of sticky hands. Syrup is practically all sugar, and it's slow-moving too. We know that our speaker isn't describing the slow-moving part of it, but by choosing the word "syrupy" at this moment, we feel like things slow down in a poem that moves very quickly.
We imagine dreams being stuck to the counter in a pool of syrup left over from last Sunday.

Maybe it just sags

Sagging things are things that are old. Floorboards sag from the weight of too many people and too much furniture over the years. Bookshelves can sag from the weight of too many books. Kindergarteners sag from the weight of backpacks that are too heavy.
The verb "sag" is directly related to the weight of something. In this way, our speaker may be pointing out just how important dreams are. They are so important that they are heavy, and if they are ignored, they will grow to sag.

like a heavy load.

The term "heavy load" reminds us of those days when we have a lot on our minds. You know those days. Someone asks you how you are doing, and all of your thoughts and worries come tumbling out of your mouth at full speed until you say, "Wow, thanks for letting me get that off of my chest."
A load is something you carry, and if it is heavy, then the going will be tough. Sometimes, others can help you carry your load, but we get the sense the speaker is referring to a load that cannot be shared or alleviated.

Or does it explode?

Just like the first line of this poem, this final line is a question all by itself. But unlike any other line in the poem, it is italicized, which makes us pay extra careful attention to it.
The word "explode" seems to us to be both a very dangerous verb and a very celebratory verb. It reminds us of both bombs and fireworks. More importantly, however, it makes us think of things that have been gathering steam and pressure over time and that can no longer suppress this energy.
In the world of this poem, this final line feels almost liberating, but also violent.