- desiccatedadjectiveChapter 1 →
Completely dried out, with all moisture removed. Here it describes the corpses of the dead crewmates, whose bodies have dried out over a long period in the spacecraft.
- zero gravitynounChapter 1 →
A condition in space where there is no effective gravitational pull, so objects and people float freely rather than being held down to a surface.
- hibernation podsnounChapter 2 →
Sealed capsules on the spacecraft designed to keep crew members in a deep, sleep-like suspended state during the long journey through space.
- AstrophagenounChapter 7 →
A fictional single-celled microorganism in the novel that feeds on solar radiation and breeds on star surfaces, draining the Sun's energy and threatening Earth with a catastrophic ice age.
“Astrophage. I named it myself. I probably shouldn't be proud of that, but I am.”
- prime numbersnounChapter 6 →
Numbers greater than 1 that can only be divided evenly by 1 and themselves, such as 2, 3, 5, and 7. In the novel they are used as a universal signal of intelligence between species.
“Any species that can make it to another star system has to understand prime numbers. That's not a guess — that's a mathematical certainty.”
- mathematical certaintyphraseChapter 6 →
Something that is guaranteed to be true based purely on the rules of mathematics, with no room for doubt or exception.
“Any species that can make it to another star system has to understand prime numbers. That's not a guess — that's a mathematical certainty.”
- starkadjectiveChapter 13 →
Harsh and impossible to avoid or soften; used here to describe a mathematical conclusion so clear and brutal that it cannot be denied or explained away.
“I'm not going to make it home. I've known it for a while, but now the math is just too stark to ignore.”
- suicide missionnounChapter 14 →
A mission that the people sending the crew know will almost certainly result in the crew's death, with no realistic plan for the crew to return alive.
“He's not a monster. He's a scared scientist who was sent on a suicide mission to save his species. Just like me.”
- one-way journeyphrase
A trip from which the traveller is not expected or able to return; a permanent departure with no planned route back.
- extinction-leveladjective
Describing a threat or event severe enough to wipe out an entire species or all life on a planet.
- sporadicadjective
Happening at irregular, unpredictable intervals rather than steadily or continuously. Used to describe how Grace's memories return in random bursts rather than all at once.
- informedverbChapter 3 →
Told someone what would happen as a statement of fact, without asking their opinion or giving them a choice. Used to show Stratt's commanding, non-negotiable style of leadership.
“Stratt didn't ask. She never asked. She informed.”
- universal languagephraseChapter 5 →
A system of communication — here mathematics — understood by any intelligent being regardless of their species, culture, or origin.
“Math. The universal language. I always knew it would come in handy someday.”
- come in handyphraseChapter 5 →
To turn out to be useful or helpful, especially in a situation where it was not originally expected to matter.
“Math. The universal language. I always knew it would come in handy someday.”
- horrifyinglyadverbChapter 7 →
In a way that causes horror or dread; used here to stress that the mathematical result is not just correct but terrifying in what it means for humanity.
“The math works. I've checked it a dozen times. The math absolutely, horrifyingly works.”
- reproduceverbChapter 7 →
To make copies of itself; to create offspring. Used here to describe the basic biological drive of the Astrophage organism.
“It's not evil. It's not trying to kill us. It just wants to eat and reproduce, same as every other living thing.”
- engineeringnounChapter 8 →
The practical work of designing and building things that function reliably, as opposed to science, which is about discovering and understanding facts.
“Science is about knowing things. Engineering is about making things work. I'm an engineer right now.”
- physiologynounChapter 11 →
The study of how a living body's parts and systems function. Here it refers to the internal workings and biological processes of Rocky's alien body.
- ammonia-based lifephraseChapter 14 →
Life forms whose chemistry is built around ammonia rather than water, allowing them to survive in environments that would be lethal to Earth creatures.
- TaumoebanounChapter 15 →
A fictional native organism found on the planet Adrian in the 40 Eridani system that naturally feeds on and destroys Astrophage, making it the key to saving Earth.
- dormantadjective
In an inactive, sleeping state, not currently operating or functioning, but capable of being started up again under the right conditions.
- probenoun
An unmanned spacecraft sent to gather information or carry a payload to a distant location, without a crew aboard.
- dockedverbChapter 12 →
Physically connected and joined to another spacecraft in space, so that the two vessels are locked together and can share access between them.
- painstakingadjective
Done with very careful, slow, and thorough effort, paying close attention to every detail so that nothing goes wrong.
- strandedadjective
Left in a place with no way to leave or return home, stuck without the means or resources to travel back.
Project Hail MaryNovel by Andy Weir