English Reference
adjective · noun · adverb

plain

adj. · n. · adv.
US /ˈpɫeɪn/ UK /plˈeɪn/ plain UK spelling plained

  1. 01 B1 Intermediate

    adj.simple and not decorated with patterns or extra details.

    adj.lacking ornament, decoration, or pattern; simple in design or appearance.

    Simple

    He wore a plain white t-shirt and blue jeans to the party.

    In context

    The interior was decorated in a plain, minimalist style that emphasised the architectural lines of the building rather than the furniture.

    simpleunadornedbasic
  2. 02 B1 Intermediate

    adj.clear and easy to see or understand.

    adj.clear to the mind; easy to perceive or understand without ambiguity.

    Simple

    The truth was plain to see for everyone in the room.

    In context

    The instructions were written in plain English to ensure that users without technical backgrounds could operate the machinery safely.

  3. 03 B2 Upper Intermediate

    adj.not beautiful or handsome, but not ugly either.

    adj.not distinguished by beauty; having a simple or unremarkable appearance.

    Simple

    She described herself as a plain person who didn't like wearing makeup.

    In context

    The protagonist was often described as a plain woman, a choice by the author to focus on her intellectual depth rather than her physical appearance.

  4. 04 B1 Intermediate

    n.a large area of flat land with few trees.

    n.an extensive area of level or gently undulating land, usually at a low elevation and often covered in grass.

    Simple

    The train travelled across the vast plains for several hours.

    In context

    The Great Plains of North America support a diverse ecosystem despite the relatively low annual rainfall and lack of natural forest cover.

  5. 05 B2 Upper Intermediate Informal

    adv.used to emphasize that something is completely true or simple.

    adv.used as an intensifier to mean 'simply' or 'completely'; typically precedes an adjective.

    Simple

    That idea is just plain stupid.

    In context

    It was plain wrong of him to take credit for work that the entire team had contributed to over the last six months.

    Usage

    Usually placed before an adjective to add emphasis.

Usage plain sight

He's not alone, from Africa's grasslands to the salt-crusted plains of Central Asia, this same story is playing out for millions of people who depend on land many people may never think about: Rangelands.

UN News· 15 Aug 2026

That’s what pulled me to the plains of north-central Spain last week.

Ars Technica· 17 Aug 2026

Etymology 1

From Middle English pleyn, borrowed from Anglo-Norman pleyn, playn, Middle French plain, plein, and Old French plain, from Latin plānus (“flat, even, level, plain”). Doublet of llano, piano, and plane.

Etymology 2

From Old French plain, from Latin plānum (“level ground, a plain”), neuter substantive from plānus (“level, even, flat”). Doublet of llano, piano, and plane.

Etymology 3

From Anglo-Norman plainer, pleiner, variant of Anglo-Norman and Old French pleindre, plaindre, from Latin plangere.

Etymology 4

From Middle English pleyn, borrowed from Old French plein, from Latin plēnus (“full, filled, complete”). Ultimately from Proto-Italic plēnos, from Proto-Indo-European pl̥h₁nós (“full”). Doublet of plene, plenary, and full.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Latin plānus
Level B2 · Upper Intermediate
Frequency Common
Updated