Least is often considered to be the superlative form of little.
1 You use at least to say that a number or amount is the smallest that is possible or likely and that the actual number or amount may be greater. The forms at the least and at the very least are also used.
at least phrase PHR amount, amount PHR
Aim to have at least half a pint of milk each day..., Normally it has only had eleven or twelve members in all. Now it will have seventeen at the very least.
2 You use at least to say that something is the minimum that is true or possible. The forms at the least and at the very least are also used.
at least phrase PHR with cl/group
She could take a nice holiday at least..., At the least, I needed some sleep..., His possession of classified documents in his home was, at the very least, a violation of Navy security regulations.
3 You use at least to indicate an advantage that exists in spite of the disadvantage or bad situation that has just been mentioned.
at least phrase PHR with cl
We've no idea what his state of health is but at least we know he is still alive..., If something awful happens to you at least you can write about it.
4 You use at least to indicate that you are correcting or changing something that you have just said.
at least phrase PHR with cl/group
It's not difficult to get money for research or at least it's not always difficult...
5 adj You use the least to mean a smaller amount than anyone or anything else, or the smallest amount possible.
the ADJ n (Antonym: most)
I try to offend the least amount of people possible..., If you like cheese, go for the ones with the least fat.
Least is also a pronoun., pron the PRON (Antonym: most)
On education funding, Japan performs best but spends the least per student.
Least is also an adverb., adv the ADV after v
Damming the river may end up benefitting those who need it the least.
6 adv You use least to indicate that someone or something has less of a particular quality than most other things of its kind.
ADV adj/adv (Antonym: most)
The least experienced athletes had caused a great many false-starts through the day's proceedings...
7 adj You use the least to emphasize the smallness of something, especially when it hardly exists at all.
the ADJ n (emphasis)
I don't have the least idea of what you're talking about..., They neglect their duty at the least hint of fun elsewhere...
8 adv You use least to indicate that something is true or happens to a smaller degree or extent than anything else or at any other time.
ADV with v (Antonym: most)
He had a way of throwing her off guard with his charm when she least expected it.
9 adj You use least in structures where you are emphasizing that a particular situation or event is much less important or serious than other possible or actual ones.
ADJ of def-n (emphasis)
Having to get up at three o'clock every morning was the least of her worries..., At that moment, they were among the least of the concerns of the government.
10 pron You use the least in structures where you are stating the minimum that should be done in a situation, and suggesting that more should really be done.
the PRON cl
Well, the least you can do, if you won't help me yourself, is to tell me where to go instead..., The least his hotel could do is provide a little privacy.
11 You can use in the least and the least bit to emphasize a negative.
in the least phrase with brd-neg, PHR with cl, PHR adj (emphasis)
I'm not like that at all. Not in the least..., I'm not in the least bit touched by the Marilyn Monroe kind of beauty..., Alice wasn't the least bit frightened.
12 You use last but not least to say that the last person or thing to be mentioned is as important as all the others.
last but not least phrase PHR with cl/group
...her four sons, Christopher, twins Daniel and Nicholas, and last but not least 2-year-old Jack.
13 You can use least of all after a negative statement to emphasize that it applies especially to the person or thing mentioned.
least of all phrase with brd-neg, PHR cl/group (emphasis)
No one ever reads these articles, least of all me..., Such a speech should never have been made, least of all by a so called responsible politician.
14 You can use not least to emphasize a particularly important example or reason.
not least phrase PHR cl/group (emphasis)
Dieting can be bad for you, not least because it is a cause of stress..., Everyone is more reluctant to travel these days, not least the Americans.
15 You can use to say the least to suggest that a situation is actually much more extreme or serious than you say it is.
to say the least phrase PHR with cl (emphasis)
Accommodation was basic to say the least..., Some members of the public can be a bit abusive to say the least.