| Word | Definition & Example |
|---|---|
| galaxy n. |
A massive system of stars, gas, and dust held together by gravity. "The Milky Way galaxy contains roughly 200 billion stars." Collocations: spiral galaxy, distant galaxy |
| orbit n. / v. |
The curved path of an object around a star, planet, or moon. "The Moon orbits Earth approximately once every 27 days." Collocations: stable orbit, orbital period |
| gravity n. |
The force that attracts objects with mass toward each other. "Gravity holds planets in their orbits around the Sun." Collocations: force of gravity, gravitational pull |
| mass n. |
The amount of matter in an object. "Jupiter has more mass than all the other planets combined." Collocations: atomic mass, total mass |
| density n. |
Mass per unit volume. "Saturn has such low density that it would float in water." Collocations: high density, density of a substance |
| radiation n. |
Energy that travels in the form of waves or particles. "Solar radiation reaches Earth in just over eight minutes." Collocations: electromagnetic radiation, harmful radiation |
| spectrum n. |
The range of colours or wavelengths into which light can be separated. "By analysing a star's spectrum, astronomers determine its composition." Collocations: electromagnetic spectrum, visible spectrum |
| wavelength n. |
The distance between two corresponding points of a wave. "Red light has a longer wavelength than blue light." Collocations: long wavelength, short wavelength |
| nebula n. |
A vast cloud of gas and dust in space. "Stars are born inside stellar nebulae." Collocations: stellar nebula, planetary nebula |
| supernova n. |
A massive stellar explosion at the end of a star's life. "A supernova outshines an entire galaxy for several weeks." Collocations: supernova explosion |
| asteroid n. |
A small rocky body orbiting the Sun. "The asteroid belt lies between Mars and Jupiter." Collocations: asteroid belt, Near-Earth asteroid |
| comet n. |
An icy body that releases gas as it approaches the Sun. "Halley's Comet returns to view from Earth roughly every 76 years." Collocations: comet's tail |
| telescope n. |
An instrument used to observe distant objects. "The Hubble telescope orbits Earth above the atmosphere." Collocations: optical telescope, radio telescope |
| constellation n. |
A group of stars forming a recognisable pattern. "Orion is one of the most easily identified constellations." Collocations: winter constellation |
| light-year n. |
The distance light travels in one year — about 9.5 trillion kilometres. "Proxima Centauri is 4.2 light-years from Earth." Collocations: many light-years away |
| velocity n. |
Speed in a particular direction. "The space shuttle reached an orbital velocity of about 28,000 km/h." Collocations: high velocity, terminal velocity |
| acceleration n. |
The rate at which velocity changes. "Earth's gravitational acceleration is approximately 9.8 m/s²." Collocations: constant acceleration |
| energy n. |
The capacity to do work or produce heat. "The Sun radiates an enormous amount of energy in all directions." Collocations: kinetic energy, potential energy |
| particle n. |
An extremely small piece of matter. "Electrons are subatomic particles with a negative charge." Collocations: subatomic particle, charged particle |
| solar system n. |
The Sun together with all the bodies that orbit it. "Our solar system formed about 4.6 billion years ago." Collocations: outer solar system |
| atmosphere n. |
The layer of gases surrounding a planet or star. "Venus has a dense atmosphere of carbon dioxide." Collocations: thin atmosphere, planetary atmosphere |
| eclipse n. |
An event where one celestial body blocks light from another. "A lunar eclipse occurs when Earth's shadow falls on the Moon." Collocations: solar eclipse, lunar eclipse |
| fusion n. |
The combining of atomic nuclei to release energy. "Nuclear fusion powers the Sun and other stars." Collocations: nuclear fusion, fusion reactor |
| expand v. |
To increase in size or volume. "Astronomical observations show that the universe is expanding." Collocations: expand rapidly |
| observe v. |
To watch carefully in order to gather information. "Galileo was the first to observe the moons of Jupiter through a telescope." Collocations: observe a phenomenon |
How this vocabulary appears on the TOEFL
Astronomy & Physics terms appear directly in passages and audio across Reading · Listening. The questions you'll see most frequently target this vocabulary are paraphrase identification (the test rewords a sentence using a synonym from this list), inference questions (you need the term's meaning to follow the argument), and reference questions (the term is the antecedent of a pronoun in another sentence). Knowing the term plus one or two natural collocations lets you decode passages faster and recognise paraphrases on the answer choices without re-reading.
How to study this list effectively
Don't try to memorise the whole list in one sitting. Effective vocabulary study works in three passes: (1) recognise — read each entry once until the word feels familiar; (2) retrieve — cover the definitions and try to recall each one from the word alone; (3) produce — write a sentence of your own that uses the word in a TOEFL context. Spaced repetition over 5–7 days will make the words stick far better than a single intensive review session. Pair this list with a practice test in the same section so you encounter the words in real test contexts.
Practise this vocabulary on real TOEFL tests
- Reading practice tests — passages on academic topics
- Listening practice tests — campus conversations and academic talks
- Full-length practice tests — vocabulary in context across all four sections
- More TOEFL vocabulary by topic