without; if it were not for
Conjunction meaning 'without' or 'if it were not for'. Often used in the pattern 〜なくして（は）〜ない, expressing that something cannot happen or exist without something else. Cross-referenced with 無くしては.
See also: なくしては
努力なくして成功はあり得ない。
Success is impossible without effort.
あなたの助けなくしては、この仕事は完成しなかっただろう。
Without your help, this work would not have been completed.
なければ is the conditional form of ない and means 'if not', while なくして is a conjunction that directly means 'without' and is used in more formal or written contexts.
without; if it were not for
Derived from the 連用形 (continuative form) of the classical adjective 無し (なし) plus the particle して, which together function as a conjunction meaning 'without'.