🤝 A shared feature ➗ A shared number

common denominator

1 3.7

A number that is a common multiple of the bottom numbers of two fractions for adding or comparing them

noun
/ˈkɑːmən dɪˈnəʊmɪneɪtər/

Specialized

: denominador común

During our math lesson, the teacher explained how to determine the common denominator for the fractions.

When you expand, constant may cancel and in this case we're left with a negative X over your LCD or common denominator.

Examples

So let's put these all over a common denominator of six.
To add the fractions one-fourth and one-third, we need to find a common denominator.
Now, who can find the common denominator of this equation?

The Great Gilly Hopkins (2015)
OK, well, we find a common denominator, and that's six.
When comparing different fractions, it is helpful to express them using a common denominator.

Synonyms

common multiple

vscommon denominator

Specialized

3.4

A number that two or more other numbers divide evenly

is the integer chosen to match denominators for adding or comparing fractions

Surface Forms

common denominator singular

common denominators plural

Morphology

common + denominator

The meaning is directly derivable from combining 'common' (shared) with 'denominator' (the bottom part of a fraction): it denotes a denominator that two or more fractions share for arithmetic operations. This is a compositional noun phrase following standard English logic (and parallels in many languages), so a B1 learner who knows both words will readily understand it.

Etymology

Common denominator is a math term: a denominator is the bottom number of a fraction and a common one is a bottom number that two or more fractions share so you can work with them together. That's why it helps you 'to add, subtract, or compare' fractions.