long是“長”,
tooth是“牙”,
long in the tooth是什么意思?
解答：
long in the tooth年紀大
“long in the tooth”的起源和馬有關。馬兒過了壯年，咀嚼能力就會衰退。咀嚼能力退化的標志是牙齦萎縮，牙根顯露出來，從而使得馬牙顯得特別長，因此人們通過檢查馬牙長短來判斷馬的實際年齡和相應的價值。所以“long in the tooth”就是指“上了年紀，年紀大”～
例句：
She's a bit long in the tooth for such a romantic role. 演這樣一個具有浪漫色彩的角色，她年紀有點太大了”
拓展知識：
有個成語叫“馬齒徒增”，意思是“空有年歲增長而學業(yè)或事業(yè)沒有長進”，可以翻譯成“to be long in the tooth with nothing accomplished”
雖然tooth是“牙齒”意思，但在一些表達中卻詮釋著不一樣的意境~
1.fight tooth and nail
釋義：
to try very hard to get something you want
竭盡全力
例句：
We fought tooth and nail to get the route of the new road changed.
我們奮力抗爭，爭取改變新修道路的路線。
2.get your teeth into sth
釋義：
to deal with something or become involved in something with great energy and enthusiasm
專注于
例句：
I'm so bored at work, I wish they'd give me something I could really get my teeth into.
我很厭倦工作，我希望他們能給我一件我能真正潛心去做的事。
3.in the teeth of sth
釋義：
If something happens or is done in the teeth of difficulties, the difficulties cause problems but do not stop it.
違抗；不顧
例句：
The road was built in the teeth of fierce opposition from the public.
這條道路是在公眾的強烈反對下修起來的。
4.set sb's teeth on edge
釋義：
If something, especially a noise, sets your teeth on edge, it annoys you very much.
（尤指噪聲）使（某人）非常惱火
例句：
That DJ's voice really sets my teeth on edge.
那位電臺音樂節(jié)目主持人的嗓音的確使我很不舒服。
