〜たが最後 (~ta ga saigo) — once ~, (it's the end / no going back)

Once that one thing happens, that's it — a bad or unstoppable result is sure to follow.

Formula (सूत्र ढाँचा)

Vた + が最後

Grammar rule (व्याकरण नियम र परिभाषा)

When to use it

Every office has one: once they start an old story, it goes on for an hour.
In speech 「〜たら最後」is a little more common.

Meaning

「〜たが最後」= 'once ~ happens, that's it — there's no stopping it, and the result is bad'.
It works both for suppositions and for habits that always happen.
What follows is always a bad, unstoppable or irreversible result: 〜まで終わらない・返事もしない・取り戻せない.

How to attach

Verb た-form + 「が最後」: 始めたが最後
「〜たら最後」means the same.

Versus what you know

N3「〜たとたん」says 'at that very moment something suddenly happened', a single event; 「たが最後」says 'after that, a bad result is certain, every time'.
N2It is close to 「〜(よ)うものなら」('if you dared to, disaster'), but that one is pure supposition.

Watch out

It is never used for a good result like 'once I took the medicine, I got better'.

Examples (उदाहरणहरू)

部長は昔の話を始めたが最後、一時間は終わらない。

ぶちょうはむかしのはなしをはじめたがさいご、いちじかんはおわらない。

Once the department head starts on stories from the old days, it goes on for at least an hour.

How it is built (कसरी बन्यो) 始める = to start → た-form: 始めた → attach 「が最後」 = once it starts, that's it → then a result that doesn't stop: 一時間は終わらない.

スマホを布団に持ち込んだが最後、朝まで動画を見てしまう。

スマホをふとんにもちこんだがさいご、あさまでどうがをみてしまう。

Once I take my phone to bed, I end up watching videos till morning.

How it is built (कसरी बन्यो) 持ち込む = to take in → た-form: 持ち込んだ → 「が最後」 = once I take it in, that's it → then a bad habit that always happens: 朝まで見てしまう.

一度うそがばれたが最後、もう誰にも信じてもらえない。

いちどうそがばれたがさいご、もうだれにもしんじてもらえない。

Once your lie is found out, no one will ever believe you again.

How it is built (कसरी बन्यो) ばれる = to be found out → た-form: ばれた → 「が最後」 → then a result that can't be undone: もう誰にも信じてもらえない.

Knowledge check (मिनी ज्ञान जाँच)

Question: 1/3

「弟はゲームを＿＿＿が最後、呼んでも返事をしない。」— fill the blank.

💡 Hint: Which verb form comes before が最後?