Mach is a way of saying how fast something is moving compared with the speed of sound, especially a fast aircraft. Mach 1 is the speed of sound. Mach 2 is twice that, and so on. People say “at Mach 2,” with the number after the name.

Mach馬赫 is a way of saying是一種說法 how fast something is moving用來表示某個東西移動得多快 compared with和...相比 the speed of sound音速, especially尤其是指 a fast aircraft快速飛行的飛機. Mach 1馬赫1 is就是 the speed of sound音速. Mach 2馬赫2 is就是 twice that音速的兩倍, and so on依此類推. People say人們會說 "at Mach 2,"「在馬赫2」 with the number after the name數字放在名稱後面.

It is not a unit like kilometres per hour on a car dashboard; it is a comparison, and the real speed of Mach 1 changes a little with the air — warmer or colder, high up or near the ground. Pilots, engineers, and news stories about jets use it.

It is not它不是 a unit像...的單位 like kilometres per hour on a car dashboard像汽車儀表板上的公里數那樣, it is它是 a comparison一種比較, and而且 the real speed of Mach 1馬赫1實際的速度 changes a little會有一點變化 with the air跟著空氣狀況 — warmer or colder較熱或較冷, high up or near the ground在高空或靠近地面. Pilots, engineers, and news stories about jets飛行員、工程師，還有關於噴射機的新聞報導 use it都會用它.

We keep a capital M because it is a person’s name used as a measure: Ernst Mach, an Austrian physicist who studied waves in air. Though actually, in loose talk someone may say “a Mach 2 jet” just to mean “very, very fast,” without doing any real sums.

We keep a capital M我們保留大寫的M because是因為 it is a person's name它是一個人的名字 used as a measure被拿來當單位用: Ernst Mach恩斯特．馬赫, an Austrian physicist一位奧地利物理學家 who studied waves in air研究空氣中波動. Though actually不過事實上, in loose talk隨口說話時 someone may say有人可能會說 "a Mach 2 jet"「一架馬赫2的噴射機」 just to mean只是想表示 "very, very fast,"「非常非常快」 without doing any real sums並沒有真的算過數字.