radius

/ˈreɪdiəs/ (bre, ipa) · /ˈreɪdiəs/ (ame, ipa) · /ˈrā-dē-əs/ (ame, mw)

radius — 名詞

  • radiussingular
  • radiiplural

1. in geometry, any line that runs from the centre point of a round shape such as a

1.名詞B1
釋義

半徑

從圓心到圓周的直線

in geometry, any line that runs from the centre point of a round shape such as a circle out to its outer boundary is called a radius; the word also names the length of that same line.

例句

Joon drew a circle with a radius of five centimetres on the board.

Joon 在黑板上畫了一個半徑五公分的圓。

radius of [measurement] for specifying size

The wheel has a radius of thirty centimetres from hub to rim.

這個輪子從軸心到邊緣的半徑為三十公分。

同義詞
  • diameter

    diameter is twice the radius, running from one edge through the centre to the opposite edge

  • half-diameter

    informal synonym for radius used in some technical contexts

文法句型

the radius of [circle/sphere]

radius of [number + unit]

用法筆記

In geometry, the plural form is radii (ˈreɪ.di.aɪ) rather than radiuses in formal contexts.

常見錯誤

❌The radius of the circle is the distance across it.
✅The radius is half the distance across it
💡the full distance is the diameter.' — Radius runs from centre to edge, not from edge to edge.

2. the measurement that tells you how far a circular area extends outward from a gi

2.名詞B1
釋義

範圍

以某點為中心周圍的區域

the measurement that tells you how far a circular area extends outward from a given location; the whole region within that distance is also described using this word.

例句

The blast from the explosion was felt within a two-kilometre radius.

爆炸的震波在兩公里範圍內都能感受到。

within a [number]-[unit] radius — common phrase for distance from a point

Padma agreed to drive anywhere within a thirty-minute radius of her home.

Padma 同意在離家三十分鐘車程的範圍內開車。

within a [time]-minute radius — extended use with travel time

同義詞
  • range

    range is more general, not necessarily circular; often used for distance a vehicle can travel or a signal can reach

  • scope

    scope focuses on the limits of what something covers rather than a physical distance around a point

  • reach

    reach suggests the furthest point you can touch or access, not the whole circular area

文法句型

within a [number]-[unit] radius of [place]

within a radius of [number] [unit]

within [number] [unit] radius

用法筆記

When used with a prepositional phrase, the pattern 'within a [measurement] radius of [place]' is the most common. Native speakers also say 'within [measurement] of [place]' without the word radius, but adding radius makes the circular shape of the area explicit.

常見錯誤

❌The hospital is at a ten-kilometre radius.
✅The hospital is within a ten-kilometre radius of the station.
💡Radius describes a circular area around a point, not a single straight-line distance to a specific location.

3. a forearm bone that runs from the elbow joint down to the wrist, sitting next to

3.名詞B2
釋義

橈骨

前臂靠拇指側的骨頭

a forearm bone that runs from the elbow joint down to the wrist, sitting next to the thumb and letting you twist your palm around.

例句

Nikos broke his radius when he tried to catch his fall on the ice.

Nikos 在冰上試圖撐住身體時摔斷了橈骨。

break one's radius — common injury collocation

The X-ray showed a clean fracture of the radius near the wrist.

X 光片顯示手腕附近的橈骨有乾淨的骨折。

fracture of the radius — medical phrasing

同義詞
  • forearm bone

    a general term covering both the radius and the ulna; less precise

  • radial bone

    formal anatomical term for the radius

反義詞
  • ulna

    the other bone in the forearm, located on the little-finger side

文法句型

the radius

fracture of the radius

break one's radius

用法筆記

This anatomical sense is often confused with the ulna, the other forearm bone. The radius is on the thumb side and is slightly shorter but wider; the ulna is on the little-finger side and extends to the elbow tip. In medical writing, the plural is radii or radiuses.

常見錯誤

❌The radius is the bone on the little-finger side of the arm.
✅The radius is the bone on the thumb side; the ulna is on the little-finger side.
💡The two forearm bones are easy to swap.