Memory tricks for science: mnemonics that work

Updated November 2026

A mnemonic is a memory cue, such as a sentence whose first letters stand for a list in order. Mnemonics are handy for remembering sequences, but they do not teach meaning, and they work best alongside regular self-testing.

What research says

A major review of study techniques (Dunlosky and colleagues, 2013) rated the keyword mnemonic, where you link a new word to a vivid image of a familiar word, as “low utility” for general use: it helps with some vocabulary-style material but is time-consuming and does not suit most subjects. The same review rated practice testing and spacing study over time as “high utility.”

First-letter mnemonics and acronyms are a different tool. They are useful for one narrow job: holding a fixed list in order. The sentence reminds you of the first letter; you still have to know what each item is. So:

Learn what each item means first, then add the mnemonic.
Test yourself: write out the full list from memory, not just the sentence.
Repeat the test after a day, a few days and a week.

Every list below has been checked. Where there is a common trap, it is noted.

Astronomy

Planets in order from the sun

My Very Educated Mother Just Served Us Nachos: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

Older versions ended with a ninth word for Pluto (often “Nine Pizzas”). The International Astronomical Union reclassified Pluto as a dwarf planet in 2006, so the list now has eight planets.

Biology

Taxonomy ranks

Dear King Philip Came Over For Good Soup: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species. Domain is the broadest rank, species the narrowest. In botany, “division” is sometimes used instead of phylum.

Phases of mitosis

PMAT: prophase, metaphase, anaphase, telophase. Many textbooks add prometaphase between prophase and metaphase, when the nuclear envelope breaks down and chromosomes attach to the spindle. Interphase comes before mitosis but is not a phase of it, and cytokinesis (the cell splitting in two) usually overlaps with telophase.

Krebs cycle intermediates

Citrate Is Krebs’ Starting Substrate For Making Oxaloacetate: citrate, isocitrate, α-ketoglutarate, succinyl-CoA, succinate, fumarate, malate, oxaloacetate. Oxaloacetate then joins acetyl-CoA to form citrate again, which is why it is a cycle. More on our Krebs cycle page.

A note on cranial nerves

The twelve cranial nerves are often taught with a mnemonic. Versions vary and several common ones are crude, so take one from your own anatomy textbook or instructor rather than a random list online.

Chemistry

Oxidation and reduction

OIL RIG: Oxidation Is Loss, Reduction Is Gain (of electrons). LEO says GER means the same thing: Lose Electrons = Oxidation, Gain Electrons = Reduction. For example, when sodium reacts with chlorine, sodium loses an electron (oxidized) and chlorine gains one (reduced).

Diatomic elements

Have No Fear Of Ice Cold Beer: hydrogen (H₂), nitrogen (N₂), fluorine (F₂), oxygen (O₂), iodine (I₂), chlorine (Cl₂), bromine (Br₂). These seven exist as two-atom molecules in their pure form. If the beer version is not right for your class, a second trick helps: apart from hydrogen, they form a “7” shape on the periodic table, starting at nitrogen (element 7), going across to fluorine, then down through chlorine, bromine and iodine.

Physics

Electromagnetic spectrum

Raging Martians Invaded Venus Using X-ray Guns: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays. In this order, wavelength gets shorter and frequency and energy get higher.

Colors of visible light

ROY G BIV: red, orange, yellow, green, blue, indigo, violet, from longest to shortest wavelength. The spectrum is continuous; the seven names are a convention, and many scientists do not treat indigo as a separate color.

Resistor color code

Big Boys Race Our Young Girls But Violet Generally Wins: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, gray 8, white 9.

Worked example for a four-band resistor: brown, black, red, gold. The first two bands are digits (1 and 0, so 10), the third is the number of zeros to add (red = 2, so 10 × 100 = 1,000 ohms), and gold means a tolerance of ±5%.

Math for science

SOH-CAH-TOA

Sine = Opposite ÷ Hypotenuse, Cosine = Adjacent ÷ Hypotenuse, Tangent = Opposite ÷ Adjacent. In a right triangle with sides 3, 4 and 5, the angle opposite the side of length 3 has sine 3 ÷ 5 = 0.6, cosine 4 ÷ 5 = 0.8 and tangent 3 ÷ 4 = 0.75.

Order of operations

PEMDAS (Parentheses, Exponents, Multiplication and Division, Addition and Subtraction) in the US; BODMAS (Brackets, Orders, Division and Multiplication, Addition and Subtraction) in the UK and elsewhere.

The left-to-right trap. Multiplication and division have equal rank, and so do addition and subtraction. Work through each pair from left to right. So 8 ÷ 2 × 4 = 4 × 4 = 16 (not 8 ÷ 8 = 1), and 10 − 3 + 2 = 7 + 2 = 9 (not 10 − 5 = 5).

Metric prefixes

King Henry Died By Drinking Chocolate Milk: kilo (1,000), hecto (100), deka (10, also spelled deca), Base unit (meter, gram, liter), deci (0.1), centi (0.01), milli (0.001).

Each step is a factor of 10. To convert, count the steps and move the decimal point that many places. Kilometers to meters is three steps to the right, so 2.5 km = 2,500 m. Milligrams to grams is three steps to the left, so 450 mg = 0.45 g.