Flat, level

• He gives plain, simple explanations.

  Tatoeba · CK · CC BY 2.0 FR

• Explain it in plain language.

  Tatoeba · sundown · CC BY 2.0 FR

Simple, unaltered.; Ordinary; lacking adornment or ornamentation; unembellished

Simple, unaltered.; Of just one colour; lacking a pattern

Simple, unaltered.; Simple in habits or qualities; unsophisticated, not exceptional, ordinary

Simple, unaltered.; Having only few ingredients, or no additional ingredients or seasonings; not elaborate, without toppings or extras

Obvious.; Evident to one's senses or reason; manifest, clear, unmistakable

Open.; Honest and without deception; candid, open; blunt

Open.; Clear; unencumbered; equal; fair

Not unusually beautiful; unattractive

Simple, unaltered.; Containing no extended or nonprinting characters (especially in plain text)rare

An expanse of land with relatively low relief and few trees, especially a grassy expanse

• The mountain rises above the plain.

  Tatoeba · orcrist · CC BY 2.0 FR

• He crossed mountains and plains.

  Tatoeba · sundown · CC BY 2.0 FR

A broad, flat expanse in general, as of water

Synonym of field in reference to a battlefieldrare

A lamentationrare

Simply

Plainly; distinctly