raio
/ˈʁaj.u/masculine
The English word 'radius' is raio in Portuguese.
raio is a masculine noun used to refer to the length of a line segment. You may also see the phrase num raio de, which is used to describe a distance or area surrounding a central point, much like the English 'within a radius of'.
Meaning: length of this line segment (noun)
Is it said differently in some regions?
In Brazil, raio is universally used and understood in both formal and informal contexts.
How do you pronounce it?
The word is pronounced /ˈʁaj.u/. It has two syllables, and the stress is on the first syllable.
Did you know?
- In Portuguese, raio is also the word for 'lightning bolt'. If you hear someone shout Caiu um raio!, they are reporting a lightning strike, not a mathematical circle.
- In some Portuguese contexts, raio can be used as a mild, old-fashioned exclamation of frustration, similar to saying 'blast!' in English.
- If you call someone an 'um raio', you might be describing a person who is incredibly fast or energetic.
Examples in context
- O raio da Terra é de aproximadamente 6.000.000 metros.The Earth's radius is approximately 6,000,000 meters.This sentence is useful for stating the radius of the Earth using raio.Tatoeba #2152754 by alexmarcelo, translation #10054432 by Nylez
- O horizonte de muitas pessoas é um círculo de raio zero e eles chamam a isso o seu ponto de vista.The horizon of many people is a circle with a radius of zero – and they call it their point of view.This sentence uses raio to describe a circle with a radius of zero.Tatoeba #10957154 by Cangarejo, translation #5226091 by Hybrid
- Acompanhando os rapazes nos seus passeios, ele aprendeu a orientar-se na vizinhança e, em pouco tempo, estava perfeitamente familiarizado com todas as ruas, bosques e campos num raio de duas ou três milhas.By accompanying the boys in their rambles he learned his way about the neighbourhood, and was in a short time perfectly acquainted with all the lanes, woods, and fields within a radius of two or three miles.This sentence uses raio to describe an area within a specific distance.Tatoeba #12034386 by Cangarejo, translation #12034385 by Cangarejo
- O raio de uma circunferência é sempre a metade do seu diâmetro.The radius of a circumference is always half of its diameter.
- 1 more sentences on Tatoeba
Example conversation
Camila and Rodrigo are looking at a mathematical diagram in a textbook.
- CamilaQual é o valor do raio deste círculo?What is the value of the radius of this circle?
- RodrigoO raio parece ser de cinco centímetros.The radius seems to be five centimeters.
- CamilaVocê pode medir o raio para confirmar?Can you measure the radius to confirm?
- RodrigoSim, eu vou medir agora.Yes, I will measure it now.
Sources
- Wiktionary, “radius” translations and entries raio, CC BY-SA 4.0, dump of 2026-09-26.
- Example sentences: Tatoeba CC BY 2.0 FR.
