adjective
plain
Simple and without decoration or added features.
The plain white ceramic mug sits beside an ornately patterned mug.

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
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.
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.