piece of paper, sheet of paper = kartka papieru

blank piece of paper?

Source: http://blog.entrepreneurthearts.com/category/entrepreneur-the-arts/entrepreneurial-tool-box/creative-support-entreprenurial-development-entrepreneur-the-arts/

kartka papieru

English sentence and Polish translation

He wrote a note for her on a sheet of paper. = On napisał dla niej wiadomość na kartce papieru.