Saskatchewan, a Canadian province, was selected by Eva Stratt as the landing site for the ArcLight probe's sample return capsule, chosen for its high latitude, flat terrain, and proximity to San Francisco, demonstrating Stratt's unilateral authority over international space operations.

The South China Sea serves as the primary operational base for Project Hail Mary, where the international scientific team, led by Eva Stratt, conducts the dangerous Astrophage breeding experiments aboard the Chinese aircraft carrier PLAN Gansu, nicknamed Stratt's Vat.

The Sun is the star at the center of Earth's solar system, whose gradual dimming due to Astrophage infection drives the entire plot of Project Hail Mary. Its declining luminosity threatens all life on Earth with an ice age, mass starvation, and societal collapse, forcing humanity to build the Hail Mary and send a crew to Tau Ceti in search of a solution.

Tau Ceti is the star system that serves as the destination of the Hail Mary mission, the only star in the local cluster that remains uninfected by Astrophage despite being surrounded by infected stars, and the site where Ryland Grace discovers the Astrophage predator Taumoeba and makes first contact with the Eridian Rocky.

Threeworld is the third planet in the 40 Eridani system, a small world roughly the size of Earth's moon that serves as the Astrophage breeding ground for Rocky's home star. Its significance lies in its thin but persistent carbon-dioxide-rich atmosphere, which makes it the target for the nitrogen-resistant Taumoeba strain that Grace and Rocky develop to save Erid from Astrophage infestation.

The Hail Mary's centrifuge is an artificial gravity system that splits the ship into two halves connected by cables, allowing the crew compartment to spin and simulate Earth-like gravity for sensitive laboratory equipment.

The Generator is the Hail Mary's primary power source, converting Astrophage into electricity through a controlled reaction that exploits the microbe's mass-energy conversion capability. Its failure during the Adrian crisis nearly kills Grace and Rocky, and its subsequent contamination by Taumoeba forces a complete power loss that threatens the entire mission.

Rocky's spaceball is a custom-built, xenonite geodesic sphere that serves as a mobile life-support system, allowing the Eridian engineer Rocky to survive inside the Hail Mary's human-friendly environment. It is a critical piece of technology that enables the first face-to-face interaction between the two species, and its design—incorporating a life-support device, magnetic locomotion, and a transparent shell—reflects the profound differences between Eridian and human biology while also symbolizing the trust and cooperation that define their partnership.

The star map model is a xenonite cylinder sent by the Eridian Rocky to communicate his origin and purpose to Ryland Grace. It is a three-dimensional map of local stars centered on Tau Ceti, with a filament connecting Tau Ceti to 40 Eridani, revealing that Rocky's species comes from the 40 Eridani system and is also threatened by Astrophage. This object is the first successful cross-species communication device, establishing that both parties share the same mission to understand why Tau Ceti is immune to Astrophage.

The U.S. Senate is the upper chamber of the United States Congress, which in the world of Project Hail Mary plays a critical role in the legal and political framework that enables Eva Stratt to exercise near-absolute authority over the global response to the Astrophage crisis. Its most consequential action is the ratification of an international treaty granting Stratt personal immunity from prosecution for any crime anywhere on Earth, a move that effectively places her above the law and allows the Hail Mary project to proceed without legal hindrance.

The U.S. Air Force is the American military service that, under the extraordinary authority of Eva Stratt, provides rapid intercontinental transport for key Project Hail Mary personnel and executes the nuclear strike on Antarctica ordered by climatologist François Leclerc to release methane and buy Earth time against the Astrophage-driven cooling.

The Royal Canadian Air Force (RCAF) is a military service that, during the Astrophage crisis, operates under the authority of Eva Stratt's Petrova Taskforce, executing missions such as recovering the ArcLight sample capsule in Saskatchewan and transporting personnel and equipment across continents, while also being subject to Stratt's preemptive legal protections and involved in the nuclear strike on Antarctica.

The Chinese Government is a sovereign state actor that, along with other nations, participates in the international response to the Astrophage crisis. It is a member of the United Nations and contributes to the Petrova Taskforce, providing military resources and industrial capacity to the Hail Mary Project, while also navigating internal political and legal challenges.

The Intellectual Property Alliance is a coalition of copyright holders, patent owners, and software industry representatives that filed a lawsuit against Eva Stratt and Project Hail Mary for the unauthorized copying of every copyrighted software program, book, and literary work onto the Hail Mary's data array, as well as for the violation of numerous patents. The lawsuit, heard in the United States District Court for the Western District of Washington, represents the most significant legal challenge to Stratt's unprecedented authority, and its swift dismissal by Stratt—who produced a preemptive pardon from the U.S. president and an international treaty granting her personal immunity from prosecution—demonstrates the complete subordination of intellectual property law to the exigencies of the Astrophage crisis.

The Central Intelligence Agency (CIA) is a U.S. intelligence agency that, during the Astrophage crisis, was conscripted by Eva Stratt to provide supercomputing resources and analytical support for Project Hail Mary, most notably by back-calculating the historical dimming patterns of local stars to trace the spread of Astrophage through the galaxy.

Astrophage and the Sun's parasitic relationship is the central ecological crisis of Project Hail Mary: a single-celled alien organism that absorbs the Sun's energy output, converts it into mass via neutrino-based storage, and uses it for propulsion, causing an exponential dimming that threatens all life on Earth within decades.

Grace and Rocky's friendship is the emotional and collaborative core of Project Hail Mary, transforming a solitary suicide mission into a cross-species partnership that saves two worlds. Beginning with cautious first contact, their bond deepens through shared trauma, mutual scientific discovery, and an unwavering commitment to each other's survival, ultimately proving that intelligence and compassion can bridge any biological or cultural divide.

The Earth-Culture Naming Rule is an informal principle invoked by Ryland Grace during his first-contact dialogue with the Eridian Rocky, asserting that the person who first discovers a place or object earns the right to name it. Grace deploys the rule to delegate the naming of the planet Tau Ceti e to Rocky, who had surveyed the system before the Hail Mary arrived. The rule reflects Grace's characteristic blend of pedagogical authority, cultural self-awareness, and diplomatic instinct, and it becomes a recurring motif in the cross-species relationship, later echoed when Grace names the Taumoeba predator and when Rocky names the color green.

The Eridian Culture Watch Rule is a deeply ingrained social norm among Eridians that requires one individual to observe another while they sleep. This practice, rooted in their biological vulnerability during sleep—when they are completely paralyzed and unable to wake—has evolved into a cultural imperative that transcends mere practicality, becoming a fundamental expression of trust, care, and social bonding.

Stratt's Redundancy Rule is a strict operational protocol Eva Stratt enforces during Project Hail Mary: no crewmember and their backup may ever share the same plane, helicopter, or car, because a single accident could eliminate both the primary and the replacement for a critical position, thereby jeopardizing humanity's only hope of survival.

Loneliness is the defining psychological condition of Ryland Grace's interstellar mission, a state that transforms from a practical consequence of crew loss into a profound existential burden that shapes every decision he makes and ultimately deepens his bond with the alien Rocky.

The Earth day is the fundamental unit of time used by Ryland Grace and the Hail Mary mission, defined as 86,400 Earth seconds and 365.25 Earth days per year. It serves as the baseline for all human timekeeping in the story, against which the urgency of the Astrophage crisis, the duration of the interstellar voyage, and the comparative lifespans and time systems of the Eridians are measured.

Danny Torrance's flight from the hedge animals is a pivotal action sequence in which the Overlook Hotel's supernatural power manifests directly in the physical world, transforming the topiary into mobile predators that pursue him across the snow-covered grounds. This event marks the collapse of Danny's hope that the hotel's horrors are merely visions, and it forces the Torrance family to confront the reality that the Overlook is actively hunting them.

Dick Hallorann battles a hedge lion that comes to life and attacks him on the road to the Overlook Hotel, a confrontation that tests his courage and resourcefulness as he fights for his life against a supernatural adversary.

Jack Torrance discovers a large wasps' nest while reshingling the Overlook Hotel's roof, is stung, and later uses a bug bomb to kill the nest. The wasps return, stinging Danny severely, which shatters the family's fragile peace and reveals the hotel's malevolent influence.

Jack Torrance breaks Danny's arm in a drunken rage, an act that becomes the defining wound of the Torrance family, the secret that haunts every subsequent relationship, and the event that the Overlook Hotel later exploits to drive Jack toward murder.

The Overlook Hotel's aging boiler, neglected by Jack Torrance during his psychotic breakdown, explodes in a catastrophic blast that destroys the building and the malevolent force within it, allowing Danny, Wendy, and Dick Hallorann to escape.

Wendy Torrance stabs Jack with a kitchen knife to defend herself and her son Danny after Jack, possessed by the Overlook Hotel, attacks her with a roque mallet.

The Wagon is a central metaphor in Jack Torrance's internal monologue, representing his fraught and ultimately failed attempt at sobriety. It begins as a glorious parade float promising escape from the gutter of alcoholism, but transforms into a nightmarish prison of enforced piety and repression, revealing Jack's deep ambivalence toward his own recovery and foreshadowing his inevitable relapse.

Danny Torrance's vision of REDRUM is a pivotal precognitive episode in which the five-year-old boy, while waiting for his father on a Boulder street corner, slips into a trance and witnesses a series of terrifying images from the Overlook Hotel's future: a blizzard, a menacing figure with a mallet, a dead woman in a bathtub, and the cryptic word "REDRUM" flashing in green fire. This vision establishes the central supernatural threat of the novel and introduces the word that will haunt Danny throughout his stay at the Overlook.