語源root, radi (根、光)の英単語の意味まとめ





eradicate /ɪrˈædəkèɪt/ : 完全に消す

eradicateは「完全に消す」を意味し、語源はex(外)とradix(根)に由来し、原義はラテン語のeradicare(根を引き抜く)です。同義語はremove, get rid of, eliminate, wipe outです。



Eradicate means “to completely remove something”, the etymology comes from ex (out) and radix (root), and the original meaning is Latin eradicare (to extract root). Synonyms are remove, get rid of, eliminate and wipe out.

Eradicate is used for bad things such as sickness and social problems. Let’s see example sentences.

Herbicides can eradicate weeds. SNS strives to eradicate offensive or discriminatory remarks. The police are conducting a campaign to eradicate gangsters. It is very difficult to eradicate racial discrimination.

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radar /réɪdɑɚ/ : レーダー

radarは「レーダー」を意味し、語源はRadio Detecting and Rangingの頭字語に由来します。例文を見てみましょう。



Radar means “equipment to find something with radio waves”, and the etymology comes from the acronym for Radio Detecting and Ranging. Let’s see an example sentence.

Radar is a device that measures the distance from the time it takes for radio waves to be reflected. On the other hand, sonar has the same principle and uses sound waves for measurement. Signals received by the radar are displayed on the PPI scope.

Weather radar is installed in 20 locations in Japan and they inform you about weather information through media. In addition, the radar detector detects a device that regulates the speed violation of the car and notifies the driver.

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radial /réɪdiəl/ : 放射状の




Radial means “having a shape like lays”, and the etymology comes from radius (wheel spokes). Radial is used for technical terms in the industrial field. Let’s see example sentences.

Radial tire or radial ply tire is one of the design of automobile tires. The merit of radial tire is its excellent durability and high safety. For that reason most cars are using radial tires.

Radial engines have been used on older fighter planes and are not used much now. Radial fans are used to send gas at the factory.

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radiant /réɪdiənt/ : 幸せに満ちた

radiantは「幸せに満ちた」を意味し、語源はradiare(輝く)に由来し、同義語はcheerful, brightです。例文を見てみましょう。


Radiant means “full of happiness”, the etymology comes from radiare (to shine), synonym is cheerful and bright. Let’s see example sentences.

A radiant bride is a woman’s envy. A very happy person always has a radiant look. Children loved by their parents will have a radiant smile.

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radiate /réɪdiət/ : 放射する

radiateは「放射する」を意味し、語源はradiare(光を放つ)に由来し、同義語はemit, send out, give off, releaseです。例文を見てみましょう。


Radiate means “to send out heat or light”, the etymology comes from radiare (to shine), its synonyms are emit, send out, give off and release. Let’s see an example sentence.

A computer with a load radiates heat. The sun radiates heat and light. The speaker radiates sound. Radioactive substances such as uranium and plutonium radiate radioactivity.

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radiation /ˌreɪdiˈeɪʃən/ : 放射線、放射能




Radiation means “harmful energy made from nuclear reaction” and the etymology comes from radius (beam of light). Let’s see an example sentence.

Radioactive substances such as uranium and plutonium emit radiation. Radiation is harmful to living things. Human five senses can not detect radiation, so we measure radiation with a specific device.

Radiation exposure means that human body receives radiation. Humans with radiation exposure will suffer from radiation damage such as cancer.

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radical /rˈædɪk(ə)l/ : 根本的な、過激な

radicalは「根本的な」を意味し、語源はradicalis(根を持つ)に由来し、同義語はfundamental, basic, drasticです。例文を見てみましょう。




Radical means “having big importance”, the etymology comes from radicalis (rooted), synonyms are fundamental, basic, drastic. Let’s see example sentences.

The Internet has brought about radical changes in our lives. Japan’s social security system requires radical reform. Social withdrawal may needs a radical solution such as kicking out from the house. There is a radical difference in the way of thinking between the rich and the poor.

The second meaning of radical is “be against most people’s thought”, the synonym is extreme, and the antonym is conservative. Let’s see example sentences.

In a peaceful society, radical politicians can not gain public support. Because the people basically do not like radical changes. It is radical idea that Japan should possess nuclear weapons.

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radio /réɪdioʊ/ : ラジオ




Radio means “a piece of instrument to listen to broadcasts”, and the etymology comes from radius (light streak). Let’s see an example sentence.

Radio is a device for listening to audio and music wirelessly. Decades ago people turned on the radio, listening to music and news. Most cars are equipped with car radios.

Radio has two methods of AM and FM. AM radio is easy for radio waves to reach, it is used to transmit news and traffic information. On the other hand, FM radio has good quality of sound, so it is suitable for broadcasting music programs.

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radioactive /rèɪdioʊǽktɪv/ : 放射能の



Radioactive means “containing radiation”, and the etymology comes from radius (beam of light) and actif (active). Let’s see an example sentence.

Radioactive substances such as iodine, cesium and strontium are harmful to the human body. Nuclear accidents cause serious radioactive contamination. The Japanese government and TEPCO deal with radioactive leakage properly. Radioactive waste must be properly handled so as not to adversely affect human beings.

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radish /rˈædɪʃ/ : 二十日大根

radishは「二十日大根」を意味し、語源はradicem(根)に由来します。日本でよく食べられる白い大根はJapanese radishと呼ばれます。例文を見てみましょう。


Radish means “a small vegetable with red roots”, and the etymology comes from radicem (root). The white radish often eaten in Japan is called Japanese radish. Let’s see an example sentence.

Radish can be eaten mainly as raw or pickled. Grated radish has the effect of neutralizing the smell of fish and helping digestion. Granted radish made with sharp radish grater is delicious. Yellow pickled radish is a food that pickled radish with bran and salt.

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radius /réɪdiəs/ : 半径




Radius means “the distance between center of circle and its circumference”, and the etymology comes from Latin radius (wheel spokes). Let’s see an example sentence.

The diameter is twice the length of the radius. In mathematics, we denote the radius as “r”. It we multiply the circumference rate by twice the radius, we get the length of the circumference.

Furthermore, if we multiply the square of radius by the circle ratio, we get the area of circle. Elementary school students draw circles with a radius of 5 cm with compass.

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root /rúːt/ : 根





Root means “a part of plant under the ground”, and its etymology comes from rot (roots) of old English. Let’s see an example sentence.

Root is one of plant organs, it has the role of absorbing moisture and nutrients and supporting the plant body. Dicotyledonous plants have a main root and lateral roots, and monocotyledonous plants have a beard root. Radish, carrot, burdock, sweet potato are classified as root vegetables.

The second meaning of root is “main cause of problem”. Let’s see an example sentence.

The root cause of obesity is a lifestyle. The root cause of lung cancer is smoking. Human desire is the root of all evil. If an accident occurs at the factory, the responsible person will investigate the root of the accident.

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