表示詞與詞、詞與句關系的詞。
常用介詞：on、at、in、、by、with等；
合成類介詞：、、onto、out of、 等；
短語類介詞： to、 of、 with等。
一、含義
介詞是一種用來表示詞與詞,詞與句之間的關系的詞。在句中不能單獨作句字成分。介詞后面一般有名詞代詞或相當于名詞的其他詞類，短語或從句作它的賓語。介詞和它的賓語構成介詞詞組，在句中作狀語，表語，補語或介詞賓語。
二、分類
1.常用簡單介詞：
, , , , , at, , , , by, , , , , , , down, for, from, past, than, , 等。
2.合成介詞：
, , onto, out of, 等。
3.短語介詞：
to, of, with, as for, of, be of, due to, in of, on of, to, with to 等。
三、介詞與“……的”之關系
在英語學習中，一遇到“……的”，大家就會立刻想到’s 所有格或者of。實際上，在很多情況下，“……的”必須借助于介詞才能準確表達。
● 美國的冬天→ the in
● 停車場的入口→ the to the lot
● 穿過森林的小路→ the path the
● 魯迅的著作→ the by Lu Xun
● 水中的月亮→ the moon in
● 歷史的見證→ the to
● 對愛的渴望→ a for love
● 對我們不利的證據→ the us
● 陽光下的漫步→ a walk in the
● 追求名譽的女人→ a lady fame
● 兩人之間的爭論→ an the two
四、重要介詞的重要用法
(1)from：此介詞表示“to”相反的方向。
He came from .
He went to .
二詞常搭配使用“from... to...”
We from to .
He'll from to .
經典用法：
● 由于→ The girl is from fear.
● 免除→ are free from care. 流浪漢們總是無憂無慮。
● 分開→ The from each at the .
● 由……制成→ The red wine is made from . 紅葡萄酒是由葡萄制成的。
由from引導的慣用法：
from far 從遠處
from now / then on 從現在/那時起
from bad to 每況愈下
from time to time( 時而)
習語：
She to me from time to time.
(2)out of：表示與"into"相反的語意。
He will be out of town.
I out of the dark room.
out of+ 名詞 (= lack, to be 用完，用光)
He went to the shop he was out of .
out of date (= old- 過時的)
The book has been out of date.
out of work (= 失業的)
He be is out of work.
out of the (= 不可能的)
the hard work is out of the .
out of (= 毫無疑問的)
That he can do it well is out of .
out of (= not 失靈的)
Her is out of , so she can't to it.
(3)by：表示從旁經過或在……附近。
He by me .
He by the sea.
經典用法：
● 通過→This is the road by they came.
● 在……時候→The man by day and by .
● 由……所生→He has two sons by her wife.
● 抓住→She her by his coat in the .
● 按……計算→The sell by the .
● 就(氣質，特征)而言→He is an by (氣質).
用于被動語意，導出動作執行者：
The was by the boy.
by + 具體時間：
They have by 8 o'.
by + 交通工具 (bus, , plan...)：
He to by air/.
by the end of + 時間名詞：到……末為止
By the end of last year, they had 100 .
By the end of this term, they will have 100 .
by then：到那時
He will in 1999, by then he will .
by way of (= via)：經由，取道
They are to the by way of Hong Kong.
by the way：順便問
By the way, do you know Mr. Li has gone?
by far：……得多(用于修飾比較級和*高級)
The book is by far the best on the .
by ：不小心，與on (故意地)語意相反
The was put into the by .
