Why do JLPT N1 learners confuse とっさに with いざ?

Both words occupy adjacent semantic territory, which is exactly why the JLPT uses them as distractors for each other on multiple-choice items. The fastest way to stop confusing them is to study them as a pair, write a one-sentence contrast in your own words, and drill the pair specifically rather than each word in isolation.

Is とっさに or いざ more common on JLPT N1?

Both appear in the JLPT N1 curriculum and either may show up on a given exam. Don't try to predict which one the test will choose — learn to distinguish them and you'll be safe regardless. Both belong to the General Expressions (1) theme of N1 vocabulary.

How do I practice this confusion pair?

Free option: visit /try and pick a confusion drill. Paid option: none — JLPT Mastery is free during launch. Whichever route you take, the engine specifically re-tests pairs you've gotten wrong rather than rotating through general vocabulary review.

JLPT N1 · Advanced · Meaning confusion

とっさに vs いざ

Q: What's the difference between とっさに and いざ?

とっさに (とっさに) means "at once" and いざ (いざ) means "now; come (now); well; crucial moment". Both relate to critical timing. とっさに refers to a reflex-like action at a specific moment, while いざ describes the 'crucial moment' itself or serves as a call to action ('now then') when that moment arrives.

Why JLPT N1 learners mix up とっさに (とっさに, “at once”) and いざ (いざ, “now; come (now); well; crucial moment”).

とっさに

at once

adverb

いざ

now; come (now); well; crucial moment

adverb

Theme: General Expressions (1)JLPT N1

Why these get confused

Both relate to critical timing. とっさに refers to a reflex-like action at a specific moment, while いざ describes the 'crucial moment' itself or serves as a call to action ('now then') when that moment arrives.

How to tell them apart

Anchor on the meaning, not the form. とっさに (at once) and いざ (now; come (now); well; crucial moment) live in adjacent semantic territory. Memorize the boundary, not just each word.
Read the example sentences below. Seeing each word in its natural context builds a faster lookup than studying the dictionary form alone.

In a sentence

とっさに (at once)

あなたにとって、男らしさって何？
中国の人って、朝ご飯に何を食べてるの？

いざ (now; come (now); well; crucial moment)

いざという時役に立つよ。
何もかも洗いざらい言ってしまえ。

How JLPT tests this pair

On JLPT N1, this pair shows up as a vocabulary meaning question. You see one word and pick its English equivalent from four options — one of which will be the other word in this pair, chosen as a distractor precisely because of the overlap.

Sample item

「とっさに」の意味は？