Having resemblance or similitude; similar; without difference. [1913 Webster]
"The darkness and the light are both alike to thee." [1913 Webster]

   In the same manner, form, or degree; in common; equally; as, we are all alike concerned in religion. [1913 Webster]

alike, adj. & adv.
--adj. (usu. predic.) similar, like one another; indistinguishable.
--adv. in a similar way or manner (all were treated alike).

Etymology:
ME f. OE gelic and ON gl{iacute}kr (LIKE(1))

N  similarity, resemblance, likeness, similitude, semblance, affinity, approximation, parallelism, agreement, analogy, analogicalness, correspondence, homoiousia, parity, connaturalness, connaturality, brotherhood, family likeness, alliteration, rhyme, pun, repetition, sameness, uniformity, isogamy, analogue, the like, match, pendant, fellow companion, pair, mate, twin, double, counterpart, brother, sister, one's second self, alter ego, chip of the old block, par nobile fratrum, Arcades ambo, birds of a feather, et hoc genus omne, gens de meme famille, parallel, simile, type, image, photograph, close resemblance, striking resemblance, speaking resemblance, faithful likeness, faithful resemblance, similar, resembling, like, alike, twin, analogous, analogical, parallel, of a piece, such as, so, homoiousian, connatural, congener, allied to, akin to, approximate, much the same, near, close, something like, sort of, in the ballpark, such like, a show of, mock, pseudo, simulating, representing, exact, lifelike, faithful, true to nature, true to life, the very image, the very picture of, for all the world like, comme deux gouttes d'eau, as like as two peas in a pod, as like as it can stare, instar omnium, cast in the same mold, ridiculously like, as if, so to speak, as it were, as if it were, quasi, just as, veluti in speculum, et sic de similibus, tel maitre tel valet, tel pere tel fils, like master, like servant, like father, like son, the fruit doesn't fall far from the tree, a chip off the old block.