in any case other than that; except that; except if: unless it rains, the game will be played
except; save: nothing can help him, unless a miracle
See unless in American Heritage Dictionary 4
(ŭn-lĕsˈ)
conjunction
Except on the condition that; except under the circumstances that: “Exceptional talent does not always win its reward unless favored by exceptional circumstances”(Mary Elizabeth Braddon).