# complementary

/ˌkɑmpɫəˈmɛntɹi/ (US) · /kˌɒmplɪmˈɛntəɹi/ (UK)

Source: https://englishreference.com/word/complementary
Updated: 2026-06-20

## Senses

### 1. completing each other

adjective · CEFR B2

describing two things that work well together because they each provide what the other is missing.

For teachers: acting as a complement; completing a whole or enhancing the qualities of another through contrast or addition.

- The two sisters have very different but complementary personalities.
- The merger was successful because the two companies possessed complementary strengths in manufacturing and digital marketing.

Usage: Often used with the preposition 'to'.

### 2. genetics

adjective · CEFR C1 · Technical

describing how parts of DNA or RNA fit together perfectly like a puzzle.

For teachers: relating to the specific pairing of nitrogenous bases in DNA and RNA molecules.

- In DNA, the base adenine is always complementary to thymine.
- The double-helix structure relies on complementary base pairing to ensure that genetic information is copied accurately during replication.

### 4. opposite colours

noun · CEFR B2

one of two colours that look very different but look good together, like red and green.

For teachers: one of a pair of primary or secondary colours that, when combined, create a neutral colour like grey or white.

- She chose orange as a complementary to the blue walls of the room.
- The artist used a vibrant purple as a complementary to the yellow highlights, creating a sense of visual tension in the portrait.

### 5. geometry

noun · CEFR C1 · Technical

an angle that, when added to another angle, makes exactly 90 degrees.

For teachers: an angle that adds with another to equal 90 degrees or a right angle.

- If one angle is 30 degrees, its complementary is 60 degrees.
- The architect calculated the complementary of the roof's pitch to ensure the support beams met at a perfect right angle.

## Examples

- The red wine is a complementary drink for this meal.
- Blue and orange are complementary colors that create strong visual contrast.
- The two policies are complementary, addressing different aspects of the same social problem without overlapping in their specific mandates.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.