A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.

For questions that require answers based on hard science, not magic or pseudo-science, but do not require scientific citations. Contrast with the hard-science and reality-check tags. Do not use this t…
Asks if a given concept is realistic in a given context. Answers should say yes or no, with supporting info. Compare this with the science-based and hard-science tags. This tag should never be the onl…
For questions about living things. Does not exclude aliens, but additional information is usually necessary (consider using "xenobiology" instead).
For questions that have to do with magic, as opposed to science/technology. Remember to explain any limits.
For questions regarding the viability of a life-form design. These questions should focus on biologically plausible creatures.
For questions dealing with how sentient beings interact with each other in a community.
For questions about the creation, use, and application of all types of technology.
For questions about any large astronomical bodies classified as planets, and their effects on their systems.
For questions relating to worlds with a setting of common science-fiction.
For questions regarding the physics relevant to fictitious worlds. General physics may be off-topic.
For questions related to the effects of certain circumstances, conditions, or locality changes on war. Related tags: [civil-war], [nuclear-war], [cold-war]
For questions about the long-term change of a specific species, type of creature, or trait, usually through the process of natural selection and reproduction. Ideal questions focus on traits, not enti…
For questions about existing weapons or designing new ones.
For questions related to outer space, stellar systems, stars and other astronomical phenomena.
For questions about humans as we know them or slightly changed, their physiology, psychology, politics, society and goals.
to mark questions related to creating plausible alien biologies that may be close to or far removed from Earthly biology but within the realms of hard science.
For questions about a different and uncharacteristic species or object that has come to the world from another world. NOT for questions about extraterrestrials in their native environment.
For questions regarding wealth, trade, or financial concepts.
Requires answers backed up by equations, empirical evidence, scientific papers, other citations, etc. Contrast with: science-based and reality-check tags. This tag should never be the only tag on a qu…
840 questions
For questions about the medieval era (500-1500AD o.e.) as a whole, regardless of the location.
831 questions
For questions about an environment or aspects of it such as geographical, atmospheric or climate.
For questions about the process of traveling through space, including in orbit around a planet or moon. Consider also [spaceships]. See also the tag information (click "info") for more details on when…
For questions involving implemented theory or technology for travelling through space. Consider also [space-travel]. See also the tag information (click "info") for more details on when this tag appli…
777 questions
For questions that ask what might have happened if history had taken a different path.
734 questions
For questions regarding planets similar to Earth in most respects. This tag should be used when describing a planet that follows the rules of Earth with exceptions outlined in the question. Usually q…
689 questions
For questions dealing with the customary and artistic characteristics of a society.
674 questions
For questions about specific changes in the characteristics of the weather in a location. You should also consider the tags [weather] and [seasons].
For questions dealing with events taking place after a catastrophic event.
672 questions
For questions about the characteristics and effects of natural features on a world.
652 questions
For questions about animal life in general.
For questions dealing with the political body with authority over a nation or world and its people.
636 questions
For questions about governance of the people, including methods, effects, and interactions with the people.
633 questions
For questions relating to peoples or sentient beings that are often found in the fantasy subgenre of fiction, such as elves, dwarves, etc. This can be about their physical characteristics, their socie…
For questions about the progress of a society's technological state.
For questions about the gases which surround a planet or some other celestial body.
For questions about the universal accelerative force between all objects.
600 questions
2 3 4 5