American science fiction author and editor Lester del Rey wrote, "Even the devoted aficionado or fan—has a hard time trying to explain what science fiction is," and the lack of a "full satisfactory definition" is because "there are no easily delineated limits to science fiction."

According to Isaac Asimov, "Science fiction can be defined as that branch of literature which deals with the reaction of human beings to changes in science and technology."

Robert A. Heinlein wrote that "A handy short definition of almost all science fiction might read: realistic speculation about possible future events, based solidly on adequate knowledge of the real world, past and present, and on a thorough understanding of the nature and significance of the scientific method."

Ray Bradbury

A Little Journey

Zero Hour

Morgue Ship

Lazarus Come Forth

Jonah of the Jove-Run

Defense Mech

Rocket Summer

The Monster Maker

Asleep in Armageddon

Isaac Asimov

Youth

Let's Get Together

Clifford D. Simak

Hellhounds of the Cosmos

Message From Mars

The Street That Wasn't There

Wilbur S. Peacock

The Victory of Klon 

Destination – Death 

Planet of No-Return

Philip K. Dick

The Eyes Have It

Beyond the Door

Beyond Lies the Wub

Of Withered Apples

The Crawlers

Survey Team

Souvenir

Human Is

Meddler

Tony and the Beetles

The Gun

The Hanging Stranger

Adjustment Team

The Defenders

Fredric Brown

Hall of Mirrors

Two Timer

Keep Out

Kurt Vonnegut

2BR02B

E.M. Forster

The Machine Stops

Robert Louis Stevenson

The Strange Case of Dr. Jekyll and Mr. Hyde

Arthur Machen

The Great God Pan

H. G. Wells

The Island of Doctor Moreau

The Invisible Man

The Time Machine

The War of the Worlds

Stanley G. Weinbaum

Flight on Titan

The Lotus Eaters

A Martian Odyssey

Poul Anderson

Sentiment, Inc

John W. Campbell

The last evolution

Atomic power 

Jerry Sohl

The Elroom

Brknk's Bounty

The Ultroom Error