least \least\ l=est, a. oe. last, lest, as. l=aesast,
   l=aesest, superl. of l=aessa less. see less, a. used
   as the superlative of little.
   smallest, either in size or degree; shortest; lowest; most
   unimportant; as, the least insect; the least mercy; the least
   space.
   1913 webster

   note: least is often used with the, as if a noun.
         1913 webster

               i am the least of the apostles.    --1 cor. xv.
                                                  9.
         1913 webster

   at least, or at the least, at the least estimate,
      consideration, chance, etc.; being no less than; hence, at
      any rate; at all events; even. see however.
      1913 webster

            he who tempts, though in vain, at least asperses
            the tempted with dishonor.            --milton.
      1913 webster

            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.

   note: 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.
         1913 webster
see also:
less at least at the least however in least in the least 
least squares 

at the least
     adv : not less than; "at least two hours studying the manual"; "a
           tumor at least as big as an orange" syn: at least
           ant: at most, at most
see also:
at least at most