名詞 least:

1. something that is of no importance

形容詞 least:

1. the superlative of `little' that can be used with mass nouns and is usually preceded by `the'; a quantifier meaning smallest in amount or extent or degree

副詞 least:

1. used to form the superlative
   同義詞：to the lowest degree

1. Least of all would I lie to you.
   我最犯不上對你撒謊了。
2. Mr. Brown talks least.
   布朗先生極少說話。
3. The least noise would startle the timid child.
   最小的響聲也會嚇著這個膽小的孩子的。

least

adj.（形容詞）
little的最高級
Lowest in importance or rank.
最不重要的，地位最低的

Smallest in magnitude or degree.
最小的：在數(shù)量或程度方面最小的
Slightest or tiniest:
最輕微的：最輕的或最微小的：
例句：
didn`t care the least bit.
根本就不在乎

adv.（副詞）
little的最高級形式
To or in the lowest or smallest degree.
最小地：達到或處于最低或最小的程度
n.（名詞）
One that is the lowest or smallest in importance, rank, magnitude, or degree:
最低的事物，最小的事物：在重要性、地位、數(shù)量或程度方面最低或最小的事物：
例句：
The dinner menu is the least of my worries tonight. The least you can do is to be polite.
今晚我一點也不用擔心晚餐的菜單。你至少可以禮貌點

<習慣用語>at least
According to the lowest possible assessment; not less than:
至少：根據(jù)最低可能的判斷；不少于：
例句：
waited at least an hour.
至少等了一小時

In any event; anyway:
無論如何；不管怎樣：
例句：
You might at least answer.
你不管怎樣該給個答復

in the least
At all:
根本：
例句：
I don`t mind in the least.
我根本就不在意

least of all
Particularly not:
尤其不：
例句：
Nobody cared, least of all the manager.
沒人在意，尤其是經(jīng)理

來源：
Middle English
中古英語
from Old English lôst * see leis- 2
源自 古英語 lôst *參見 leis- 2