To weaken something slowly, from underneath, so that it finally cannot stand. The picture inside the word is literal: in old warfare, attackers dug a tunnel — a mine — under a castle wall, and when they burned the props holding the tunnel up, the wall fell down by itself. Nobody hit the wall. That is exactly how the word feels today.

from underneath從底下 slowly慢慢地 to weaken something把某個東西削弱， so that it finally cannot stand讓它最後撐不住。The picture inside the word這個字背後的畫面 is literal是很寫實的： in old warfare在古代戰爭裡， attackers攻城的人 dug a tunnel — a mine —挖了一條地道，也就是所謂的mine（坑道）， under a castle wall在城牆底下， and when they burned the props holding the tunnel up等到他們把撐住地道的柱子燒掉， the wall fell down by itself城牆就自己垮了。Nobody沒有人 hit the wall去打那面牆。That這 is exactly正是 how the word feels today這個字今天給人的感覺。

You undermine someone's confidence, their authority, their position, an argument, a peace deal, a country's economy. The damage is gradual, often hidden, and often done by someone who looks friendly on the surface — a colleague who keeps 'just checking' your work in front of the boss is undermining you, even though every single thing they say sounds helpful. That quiet, indirect quality is the heart of the word: one loud insult is not undermining; a hundred small doubts are.

You你 undermine可以undermine（削弱） someone's confidence一個人的信心、 their authority他們的權威、 their position他們的地位、 an argument一個論點、 a peace deal一份和平協議、 a country's economy一個國家的經濟。The damage這種傷害 is gradual是漸進的、 often hidden常常是隱藏的， and often done by someone而且常常是某個人做的 who looks friendly on the surface表面上看起來很友善的 — a colleague一個同事 who keeps 'just checking' your work in front of the boss在老闆面前一直「順便check一下」你的工作 is undermining you其實就是在undermine（暗中削弱）你， even though every single thing they say sounds helpful儘管他說的每一句話聽起來都很有幫助。That quiet, indirect quality這種安靜、間接的特質 is the heart of the word就是這個字的核心： one loud insult一句大聲的侮辱 is not undermining不算undermine； a hundred small doubts一百個小小的懷疑 are才算。

It also keeps its physical use — a river can undermine a bridge, waves can undermine a cliff — and there the meaning is plain: it eats away the ground underneath.

It它 also keeps its physical use也保留了字面上的用法—— a river一條河 can undermine a bridge可以undermine（掏空）一座橋， waves海浪 can undermine a cliff可以undermine（掏空）一座懸崖—— and there the meaning is plain在這裡意思很直白： it eats away the ground underneath就是把底下的地基一點一點吃掉。

Watch the grammar: it takes a direct object (undermine ME, undermine the plan), and the thing undermined is usually something abstract that stands up because people believe in it — trust, confidence, authority, credibility. Facts can also undermine a claim, which is a slightly cooler, academic use: the new evidence undermines his theory. Past tense: undermined.

Watch the grammar注意文法： it takes a direct object它後面要接一個直接受詞 (undermine ME, undermine the plan)（undermine me、undermine the plan）， and the thing undermined而被undermine的東西 is usually something abstract通常是抽象的、 that stands up because people believe in it靠人們相信才能站得住的東西—— trust, confidence, authority, credibility信任、信心、權威、可信度。Facts事實 can also undermine a claim也可以undermine（削弱）一個說法， which is a slightly cooler, academic use這是比較冷靜、學術一點的用法： the new evidence undermines his theory新的證據undermine了他的理論。Past tense過去式： undermined undermined。