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  • Adj.




Imagine the quantity of a raindrop in comparison with the volume of the ocean: that quantity is infinitesimal in size. Imagine the weight of a single grain of sand out of all the sand in the Sahara desert: that one grain of sand’s weight is infinitesimal. Furthermore, imagine a single bacterium compared with the trillions upon trillions of bacteria present on planet Earth: that, my friend, is what I mean by infinitesimal.

Quiz: What is an infinitesimal amount of something?

  • It is immeasurably small.
  • It is tiny in comparison with something else.
  • It is a significant amount of something.

Memory Hook

Infinitely Small Something infinitesimal, like an atom, is infinitely small.


  • Three years ago, astrophysicists electrified the world when they detected gravitational waves—infinitesimal ripples in space itself—set off when two massive black holes swirled into each other and merged about 1.3 billion light-years away. —Science Magazine
  • Magnets steer them, so the infinitesimal particles smash into each other, packing the energy of two buses colliding into a tiny speck of space. —NPR

Word Ingredients

in- not
fin end, form a boundary, limit
-al of or relating to

Something infinitesimal is so very small that its smallness has “no end or limit.”

Word Constellation