noun
ten-day period of a month
Used mainly in compounds and date expressions dividing a month into roughly three ten-day periods, especially 上旬, 中旬, and 下旬.
会議は六月上旬に開かれる予定です。
The meeting is scheduled to be held in early June.
中旬までに書類を送ってください。
Please send the documents by the middle third of the month.
noun
decade of age; ten-year period in one's life
Rare, old-fashioned or literary use for a ten-year span of age, typically seen in compounds such as 六旬 or 七旬 rather than as a free everyday noun.
「七旬」は、七十歳代を指す古風な表現です。
七旬 is an old-fashioned expression referring to one's seventies.