HSK 7–9 grammar · conjunction
幸亏⋯⋯，要不然/不然/要不/否则⋯⋯
幸亏⋯⋯，要不然/否则⋯⋯ — luckily …, otherwise …
Pattern
+ +
( ) can be left out · other words may come before, between and after
How it works
The first clause names the lucky circumstance; the second spells out the bad outcome it prevented. The second clause describes something that did NOT happen, so it usually carries 就 and a 了 of hypothetical completion.
Examples
幸亏你提醒我，要不然我就忘了。
Xìngkuī nǐ tíxǐng wǒ, yàoburán wǒ jiù wàng le.
Luckily you reminded me, or I'd have forgotten.
幸亏走得早，否则赶不上火车了。
Xìngkuī zǒu de zǎo, fǒuzé gǎn bu shàng huǒchē le.
Luckily we left early — otherwise we'd have missed the train.
Related
幸亏 · 幸亏 — luckily, thanks to幸好 · 幸好 — luckily要不然／不然 · 要不然／不然 — otherwise / or else否则 · 否则 — otherwise / or else
See it in a story
In the app, 幸亏⋯⋯，要不然/不然/要不/否则⋯⋯ is underlined wherever it appears in the stories you read, and practised with sentences from them. Free.