* Least is often used with the, as if a noun.

I am the least of the apostles. 1 Cor. xv. 9.

At least, or At the least, at the least estimate, consideration, chance, etc.; hence, at any rate; at all events; even. See However.

He who tempts, though in vain, at least asperses
The tempted with dishonor. Milton.

Upon the mast they saw a young man, at least if he were a man, who sat as on horseback. Sir P. Sidney.

-- In least, or In the least, in the least degree, manner, etc. "He that is unjust in the least is unjust also in much." Luke xvi. 10. -- Least squares (Math.), a method of deducing from a number of carefully made yet slightly discordant observations of a phenomenon the most probable values of the unknown quantities. It takes as its fundamental principle that the most probable values are those which make the sum of the squares of the residual errors of the observation a minimum.