Meaning trap
knock out
make someone unconscious
To hit someone so hard that they become unconscious, or to cause someone to become unconscious for a short time.
Don't mix these meanings
Same phrase, different job.
To hit someone so hard that they become unconscious, or to cause someone to become unconscious for a short time.
Another meaning of 'knock out' is 'eliminate from a competition'; compare the examples to keep the meanings separate.
Hear it in context
Notice where the phrase sounds natural.
The boxer knocked his opponent out in the second round.
During the match, one player was accidentally knocked out and had to be taken to the hospital for a check-up.
Fix the pattern
One small grammar move makes it sound right.
Not: He was knocked out unconscious.
Say: He was knocked out.
'Knock out' already means make unconscious — 'unconscious' is redundant.
Which sounds natural?
Tap the one a native speaker would say.
'Knock out' is the plain verb for being made unconscious. 'Rendered him unconscious' is formal.
Build natural chunks
Words that usually travel with it.
knock out
- cold
- with one punch
- in the ring
- the anaesthetic
Don't confuse it
Related
Other meanings and phrases to compare.
- knock out (eliminate from a competition) — Another meaning of 'knock out' is 'eliminate from a competition'; compare the examples to keep the meanings separate.