adj. 25B6; adjective
grandmother looked almost childlike : YOUTHFUL, young, young-looking, girlish, boyish.
geniuses tend to be rather childlike : INNOCENT, artless, guileless, unworldly, unsophisticated, naive, ingenuous, trusting, unsuspicious, unwary, credulous, gullible; unaffected, without airs, uninhibited, natural, spontaneous; informal wet behind the ears.