first of all

英 [fɜːst ɒv ɔːl]

美 [fɜːrst əv ɔːl]

第一;首先

牛津词典

firstly在英国英语中比在北美英语中更通用。
Firstly is more common in BrE than in NAmE .
1. The brochure is divided into two sections, dealing firstly with basic courses and secondly with advanced ones.
  小册子分为两部分：第一部分涉及基础课程，第二部分涉及高级课程。
at first用以讲述最初阶段的情况，尤指与后来的不同情况相比较：
At first is used to talk about the situation at the beginning of a period of time, especially when you are comparing it with a different situation at a later period.
1. Maggie had seen him nearly every day at first. Now she saw him much less.
  起初玛吉几乎每天都见到他，现在见到他的次数少得多了。

adv

before anything else
1. first we must consider the garter snake
Synonym:firstfirstlyforemostfirst off

First of all, could I begin with an apology for a mistake I made last week?
首先，请允许我为上周犯下的错误道歉。
First of all, I want to give you some details regarding my actual tasks.
首先，我想给你一些细节，就是我实际的工作。
First of all, I want to thank my parents for bringing me into this world.
首先，我想感谢我的父母把我带到这个世界上。
First of all, study how he is with other girls.
首先，研究一下他和其他女孩在一起是怎么样的。
First of all, there are not many of them, and secondly, they have little money and, thirdly, they have few big businesses.
首先，他们人数不多；第二，他们钱很少；第三，他们没有几家大企业。
First of all, let's set the scene.
首先让我们来叙述一下背景。
First of all, first of all, when I do business with him.
首先，首先，我和他做交易的时候。
First of all we should make primary education universal.
首先我们应普及初等教育。
First of all, I like the zoo.
首先，我喜欢动物园。
First of all, I have a passion, I will be happy to work.
首先，我有热情，我会快乐地投入工作。