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Concentric describes circles, rings, or round shapes that share the same centre. If you draw one circle, then a bigger circle around it with the same middle point, those two circles are concentric. Tree rings are concentric. A ’s rings are concentric. Ripples when you drop a stone in still water spread in concentric circles. Though actually, the word is a bit technical — you meet it in maths, science, and design more than in everyday chat. People do not call two friends concentric. It is almost always about shapes that go around one shared middle.
同心的（如同心圓）
組成con- (together, with) + Latin centrum (centre, the middle point) + -ic (adjective). So: sharing a centre. Same pieces as con- + -centric.
原始詞典資料2 筆記錄
以下是外部詞典記錄的用法，原文照列，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
concentricadj/kənˈsɛn.tɹɪk/
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geometrymathematicssciencesHaving a common center.
- Seven huge concentric semi-circular rings of stone surround the northern end, and quite rightly are Grade 2-listed by conservation body Historic England.
- The ordo amoris can be conceptualized as a series of concentric circles radiating outward from ourselves, beginning with loving God, who is, as Augustine put it, “closer to us than we are to ourselves,” and ending with loving the rest of the world outside our own country.
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medicinephysiologysciencesOf a motion, in the direction of contraction of a muscle. (e.g. the extension of the lower arm by means of the elbow joint while contracting the triceps and other elbow extensor muscles; closing of the jaw while flexing the masseter).
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。