WordNet

not elaborate or elaborated; simple; "plain food"; "stuck to the plain facts"; "a plain blue suit"; "a plain rectangular brick building"
extensive tract of level open land; "they emerged from the woods onto a vast open plain"; "he longed for the fields of his youth" (同)field, champaign
lacking embellishment or ornamentation; "a plain hair style"; "unembellished white walls"; "functional architecture featuring stark unornamented concrete" (同)bare, spare, unembellished, unornamented
not mixed with extraneous elements; "plain water"; "sheer wine"; "not an unmixed blessing" (同)sheer, unmingled, unmixed
lacking patterns especially in color (同)unpatterned
free from any effort to soften to disguise; "the plain and unvarnished truth"; "the unvarnished candor of old people and children" (同)unvarnished
unornamented; "a simple country schoolhouse"; "her black dress--simple to austerity"
any herbaceous plant having medicinal properties
(botany) of leaf shapes; of leaves having no divisions or subdivisions (同)unsubdivided
having few parts; not complex or complicated or involved; "a simple problem"; "simple mechanisms"; "a simple design"; "a simple substance"

PrepTutorEJDIC

『はっきり見える』(『聞こえる』) / 『はっきり理解できる』,明白な / 全くの(sheer) / 混ぜ物のない,生(き)のままの;飾りのない;無地の / ありのままの / 『質素な』,飾り(模様)のない / (食べ物が)淡白な / 平凡な,並みの,普通の;素朴な / 『平原』,平野;《the Great Plains》(北米の)大平原地帯
(編みもので)平編みの,基本編みで作った / 平編み,基本編み
『簡単な』容易な,分かりやすい / (複合に対して)単一の / 『単純な』,込み入っていない / 『純然たる』,全くの / 『飾り気のない』,簡素な,地味な,質素な / 『もったいぶらない』;誠実な,実直な / お人よしの,だまされやすい / 《文》地位のない,普通の,平(ひら)の
薬草,薬用植物