but just to make sure that we have the vocabulary right,

这只是为了确保我们用词正确
and some of these are words that you're familiar with like drug.

有一些词你们很熟悉例如药物
A drug is any molecule which can be introduced into the body,

药物是指能够进入身体的任何分子
which alters body function on a molecular level.

它能在分子水平上改变身体的功能
You're used to thinking about drugs

一提到的药物你们就会习惯性地想到
you might take for a headache like aspirin or Ibuprofen.

头疼时吃的阿司匹林或布洛芬
Or if you asthma, for example,

如果你有哮喘病
you might take drugs that affect your bronchioles or the pathways--

你或许需要服用能够扩张
the airways in your lung by dilating them

肺部细支气管或气道的药物
so it's easier to get air in and out.

从而使呼吸顺畅
These are molecules which are introduced into the body;

这些进入体内的分子
they make some kind of change in the body on a molecular level.

会在分子层面上引起体内发生一些变化