Where do these prefixes come from?

Latin and Greek number words, the same ones behind math terms. That is why a unicycle and a unit, an octopus and an octagon, rhyme in meaning.

How does this help outside vocabulary quizzes?

Science and math lean on these constantly: bilateral symmetry, centimeter, decade. A child who reads the number in the word is ahead in three subjects at once.

5th grade number prefixes (uni-, bi-, tri-)

5th grade number prefixes (uni-, bi-, tri-) worksheets

Fifth graders read number-prefix words as little equations and extend the family to the bigger numbers (cent-, oct-, dec-) met in math and science.

Free printable PDF worksheet, aligned to Common Core L.5.4.b.

Each print is a different sheet with its own answer key. You don't need to sign up.

The kind of words you'll complete and sort

Fill in the missing letters to make a real word, then write the whole word in its column.

ceratops (the horned dinosaur)plane (an old plane with two sets of wings)athlon (a race mixing skiing and shooting)ted (joined together as a group)cycle (two wheels and a chain)cycle (one wheel and no handlebars)te (join together)ple (a hit that lands you on third base)o (a small band: drums, bass, and guitar)

Columns: uni- (one) and bi- (two) and tri- (three). The clue (joined together as a group) picks uni for "_ted", so united goes under uni- (one); the clue (a race mixing skiing and shooting) picks bi for "_athlon", so biathlon goes under bi- (two); the clue (a small band: drums, bass, and guitar) picks tri for "_o", so trio goes under tri- (three).

Every print pulls a new set of words at this level, so a make-up test or a second sibling gets a different mix.

What's on a 5th grade sheet

5th grade sheets draw from 31 words, 21 to a page. 5th and 6th grade print from the same 31 words. What changes is the standard (L.5.4.b here) and the teaching notes below. All 24 of 4th grade's words are here too, plus 7 more.

Some of the words:

unicornuniversebilingualbimonthlybiannualbicolorbicepstripletriceratopstricycle

Complete and sort. Fill in the missing letters to make a real word, then write the whole word in its column. 21 words per page.

Every version prints on US Letter or A4, with its answer key on the last page.

How to teach this

Connect to math class: cent- in centimeter and century, tri- in triangle, oct- in octagon. Number prefixes are the one place vocabulary homework and math homework are the same homework.

Watch for: The prefix is a claim you can verify: count the wheels, sides, or parts and the word proves itself. Words that carry their own evidence are the easiest morphology in English. Uni- words hide the 'one' idea in different ways: one horn (unicorn), one outfit for all (uniform), one voice together (unison). The counting is sometimes an idea, not an object.

Common questions about 5th grade number prefixes (uni-, bi-, tri-)

Where do these prefixes come from?: Latin and Greek number words, the same ones behind math terms. That is why a unicycle and a unit, an octopus and an octagon, rhyme in meaning.
How does this help outside vocabulary quizzes?: Science and math lean on these constantly: bilateral symmetry, centimeter, decade. A child who reads the number in the word is ahead in three subjects at once.

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Aligned to Common Core L.5.4.b. Reviewed by the One more sheet team. Content version 241, updated August 2026.

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