Immediately vs We must go at once

When to use each in English, with meaning, register, and examples.

Immediately

Top 1,000 (very common)A2adverb

We must go at once

Top 2,000 (common)
Most common: Immediately
 ImmediatelyWe must go at once
Pronunciation🇬🇧 /["/ɪˈmiːdiətli/"]/🇺🇸 /["/ɪˈmiːdiətli/"]/🇬🇧 //wiː mʌst ɡoʊ æt wʌns//🇺🇸 //wi mʌst ɡoʊ æt wʌns//
Meaningright away, without waitingWe need to leave immediately.
ExampleHe answered the question immediately after it was asked.We must go at once if we want to catch the train.
RegisterNeutralNeutral
How commonTop 1,000 (very common)Top 2,000 (common)
CEFR levelA2-
Part of speechadverb
Collocationsrespond immediately, act immediately, notify immediatelygo at once, must go, leave at once
Antonymseventually, later-
Common mistakesUsing 'immediate' instead of 'immediately'., Confusing with 'eventually', which means later., Incorrectly placing 'immediately' at the end of a sentence.Confused with 'at once' vs 'right away', Using 'we must go at once' in casual contexts where simpler phrases suffice, Overusing the phrase in non-urgent situations
Usage notesUse 'immediately' to emphasize urgency or promptness. It's appropriate in both spoken and written English, but avoid in very casual contexts.Use this phrase to express urgency. It's appropriate in both spoken and written contexts, especially when time is a factor.

See it in real clips

Immediately
We must go at once

Frequently asked questions: Immediately vs We must go at once

What's the difference between Immediately and We must go at once?

Immediately: right away, without waiting We must go at once: We need to leave immediately.

Which is more common: Immediately and We must go at once?

Immediately is the most common in everyday English.

Can you show an example of each?

Immediately: He answered the question immediately after it was asked. We must go at once: We must go at once if we want to catch the train.

Can I use Immediately and We must go at once interchangeably?

Not always. Immediately and We must go at once are related and overlap in some contexts, but they differ in register, how common they are, and usage, so swapping one for another can change the meaning or tone. Check the differences above before substituting.