DictionaryplainWithout decoration
adjective

plain

Simple and without decoration or added features.

The plain white ceramic mug sits beside an ornately patterned mug.

A completely plain undecorated white ceramic mug beside an ornate patterned mug, plain object's lack of decoration clearly contrasts embellishment, no lettering.
Etymology

The source means flat or level. Freedom from surface irregularity developed into freedom from ornament or extra features, giving plain its simple, undecorated sense.

In context

The 1928 Club369:26
she would have had to buy lace, and frilling, and Lord knows what besides; and she wouldn’t have had time to make it in one night. Plain long cloth means a plain servant’s nightgown.
The Moonstone by Wilkie Collins | Part 1: The Loss of the Diamond | Full Audiobook

More examples

  • He wears a plain shirt with no logo.
  • I prefer plain yogurt with fresh fruit on top.
  • We choose the plainer curtains without the embroidered border.

Forms

plain · plainer · plainest

plainness noun — The quality of being simple or undecorated.

Similar words

simple
Emphasizes little complexity, rather than a lack of decoration.
undecorated
Specifically means lacking decoration, without implying anything about added features.