An adverb meaning 'at least'; indicates a minimum amount, number, or condition (widely used in spoken and written Japanese).
少なくとも一時間は待ってください。
Please wait for at least one hour.
資料は少なくとも三部用意してください。
Please prepare at least three copies of the materials.
彼は少なくとも来週には戻るだろう。
He will return at least by next week.