名詞 first:

1. the first or highest in an ordering or series
   同義詞：number one
2. the first element in a countable series
   同義詞：number one, number 1
3. the time at which something is supposed to begin
   同義詞：beginning, commencement, outset, get-go, start, kickoff, starting time, showtime, offset
4. the fielding position of the player on a baseball team who is stationed at first of the bases in the infield (counting counterclockwise from home plate)
   同義詞：first base
5. an honours degree of the highest class
   同義詞：first-class honours degree
6. the lowest forward gear ratio in the gear box of a motor vehicle; used to start a car moving
   同義詞：first gear, low gear, low

形容詞 first:

1. preceding all others in time or space or degree
2. indicating the beginning unit in a series
   同義詞：1st
3. serving to set in motion
   同義詞：inaugural, initiative, initiatory, maiden
4. serving to begin
   同義詞：beginning
5. ranking above all others
   同義詞：foremost, world-class
6. highest in pitch or chief among parts or voices or instruments or orchestra sections
7. being the gear producing the lowest drive speed
   同義詞：low

副詞 first:

1. before anything else
   同義詞：firstly, foremost, first of all, first off
2. the initial time
   同義詞：for the first time
3. before another in time, space, or importance
4. prominently forward
   同義詞：foremost

1. First of all she just smiled, then she started to laugh.
   最初她只是微笑，後來(lái)才放聲大笑。
2. First off, let's see how much it'll cost.
   首先，讓我們看看要花多少錢(qián)。
3. He was the first to be there.
   他是第一個(gè)到達(dá)那里的。
4. Sunday is the first day of the week.
   星期日是一周的第一天。
5. Read the text first and then explain the new words.
   先讀課文，然后解釋生詞。

first

n.（名詞）
The ordinal number matching the number one in a series.
第一：一個(gè)系列中的相配數(shù)字一的序數(shù)
The one coming, occurring, or ranking before or above all others.
首要：在到來(lái)、發(fā)生或排銜上比其它居先的
The beginning; the outset:
開(kāi)頭；開(kāi)始：
例句：
from the first; at first.
從頭開(kāi)始；起先

Music The voice or instrument highest in pitch or carrying the principal part.
【音樂(lè)】 高音部，主奏樂(lè)器：在音調(diào)上最高的聲音或樂(lè)器，或演唱或演奏主要部分
The transmission gear or corresponding gear ratio used to produce the range of lowest drive speeds in a motor vehicle.
頭檔，低速齒輪：限定機(jī)動(dòng)車(chē)輛最低駕駛速度范圍的傳動(dòng)齒輪或?qū)?yīng)齒輪的比率
The winning position in a contest:
第一名，冠軍：競(jìng)賽中處于勝利的地位：
例句：
finished the season in first.
以第一名結(jié)束了賽季

Baseball
【棒球】
First base.
第一壘
A first baseman.
一壘手
adj.（形容詞）
Corresponding in order to the number one.
第一位的：按順序排在第一位的
Coming before all others in order or location:
首先的，最前的：在順序或方位上比其它人（事）領(lǐng)先的：
例句：
the first house on your left.
在你左邊的第一間房子

Occurring or acting before all others in time; earliest:
最早的：在時(shí)間上比其它人（事）先發(fā)生或先行動(dòng)的；最早的：
例句：
the first day of spring.
春季的第一天

Ranking above all others, as in importance or quality; foremost:
第一流的：在重要性或質(zhì)量上排銜在其它之上的；最前面的：
例句：
was first in the class.
在班上數(shù)第一的

Music Being highest in pitch or carrying the principal part:
【音樂(lè)】 第一聲部的，高音部的：聲調(diào)最高的或演唱（奏）主要部分的：
例句：
first trumpet.
高音號(hào)

Of, relating to, or being the transmission gear or corresponding gear ratio used to produce the range of lowest drive speeds in a motor vehicle.
頭檔的，低速齒輪的：限定機(jī)動(dòng)車(chē)輛最低駕駛速度范圍的傳動(dòng)齒輪或?qū)?yīng)齒輪比率的或與之有關(guān)的
adv.（副詞）
Before or above all others in time, order, rank, or importance:
第一地，首要地：在時(shí)間、秩序、地位或重要性上比其他人（或物）居前或在上的：
例句：
arrived first; forgot to light the oven first.
第一個(gè)到達(dá)；忘了先點(diǎn)上爐子

For the first time.
第一次地
Rather; preferably:
寧可；寧愿：
例句：
would die first.
寧愿死

In the first place; to begin with.See Usage Note at firstly
首先；以…開(kāi)始參見(jiàn) firstly

來(lái)源：
Middle English
中古英語(yǔ)
from Old English fyrst * see per
源自 古英語(yǔ) fyrst *參見(jiàn) per