plain

nouns

extensive tract of level open land
"they emerged from the woods onto a vast open plain"; "he longed for the fields of his youth"
a basic knitting stitch

verbs

express complaints, discontent, displeasure, or unhappiness
"My mother complains all day"; "She has a lot to kick about"

adjectives

clearly revealed to the mind or the senses or judgment
"the effects of the drought are apparent to anyone who sees the parched fields"; "evident hostility"; "manifest disapproval"; "patent advantages"; "made his meaning plain"; "it is plain that he is no reactionary"; "in plain view"
is derived from
not elaborate or elaborated; simple
"plain food"; "stuck to the plain facts"; "a plain blue suit"; "a plain rectangular brick building"
antonym
is similar to
severely simple
"a stark interior"
is similar to
apart from anything else; without additions or modifications
"only the bare facts"; "shocked by the mere idea"; "the simple passage of time was enough"; "the simple truth"
is similar to
pure and simple in design or style
"a chaste border of conventionalized flowers"
is similar to
(of food) eaten without a spread or sauce or other garnish
"dry toast"; "dry meat"
is similar to
having no adornment or coloration
"dry facts"; "rattled off the facts in a dry mechanical manner"
is similar to
lacking distinguishing characteristics or features
"the featureless landscape of the steppe"
is similar to
plain and unpretentious
"homely truths"; "letters to his son full of homely advice"; "homely fare"
is similar to
not elaborate; lacking rich or complex detail
is similar to
avoiding embellishment or exaggeration (used for emphasis)
"it's the literal truth"
is similar to
unornamented
"a simple country schoolhouse"; "her black dress--simple to austerity"
is similar to
severely simple in line or design
"a neat tailored suit"; "tailored curtains"
is similar to
plain and without any extras or adornments
"the most common type of bond is the straight or plain vanilla bond"; "the basic car is known as the vanilla version"
see also
not decorated with something to increase its beauty or distinction
see also
lacking pretension or affectation
"an unpretentious country church"; "her quiet unpretentious demeanor"
see also
not rhetorical
see also
having few parts; not complex or complicated or involved
"a simple problem"; "simple mechanisms"; "a simple design"; "a simple substance"
lacking patterns especially in color
antonym
not mixed with extraneous elements
"plain water"; "sheer wine"; "not an unmixed blessing"
is derived from
free from any effort to soften to disguise
"the plain and unvarnished truth"; "the unvarnished candor of old people and children"
lacking embellishment or ornamentation
"a plain hair style"; "unembellished white walls"; "functional architecture featuring stark unornamented concrete"
is derived from
lacking in physical beauty or proportion
"a homely child"; "several of the buildings were downright homely"; "a plain girl with a freckled face"
is derived from

adverbs

unmistakably (`plain' is often used informally for `plainly')
"the answer is obviously wrong"; "she was in bed and evidently in great pain"; "he was manifestly too important to leave off the guest list"; "it is all patently nonsense"; "she has apparently been living here for some time"; "I thought he owned the property, but apparently not"; "You are plainly wrong"; "he is plain stubborn"