Un-, dis- and in- all mean not, but each word takes its own: unlocked, disagree, incorrect.
Prefixes that mean "not"
Not "I unagree with you." — say "I disagree with you.". Agree takes dis-, not un-.
Try it: Liam: Can I get into the storage room? Ethan: Yes, it's ___ until six. Choose the word for the blank. (unlocked / dislocked / inlocked) Answer: unlocked — Locked takes un- for the opposite: unlocked.
Word
Pronunciation
Example
unlocked
/ʌnˈlɑkt/
not locked: Lars left the bike shed unlocked.
disagree
/ˌdɪsəˈɡriː/
not agree: Lars disagreed with the final decision.
incorrect
/ˌɪnkəˈrekt/
not correct: The answer was incorrect.
When in- changes its spelling
Before p, b or m, in- becomes im-; before l it becomes il-; before r it becomes ir-.
Try it: Diego: Can I drive through the old square? Yasmin: No, that's ___. The square is closed to cars. Choose the word for the blank. (illegal / unlegal / inlegal) Answer: illegal — Legal takes in-, which becomes il- before l: illegal.
Word
Pronunciation
Example
impossible
/ɪmˈpɑːsəbl/
not possible: It is impossible to finish the report in one hour.
illegal
/ɪˈliːɡl/
not legal: Parking on the bridge is illegal.
irregular
/ɪˈreɡjələr/
not regular: "Go" is an irregular verb.
incomplete
/ˌɪnkəmˈpliːt/
not complete: The form was incomplete, so Yasmin sent it back.
Again and before
Re- means again, as in rewrite, and pre- means before, as in prearrange.
Not "My essay needs work, so I have to prewrite it." — say "My essay needs work, so I have to rewrite it.". Re- repeats something already done, and pre- happens in advance.
Try it: Hiroshi: Did you hear the end of the podcast? Mei: I missed it the first time, so I ___ the last part. Choose the word for the blank. (replayed / preplayed / displayed) Answer: replayed — Re- means again, so playing it a second time is replayed.
Word
Pronunciation
Example
rewrite
/ˌriːˈraɪt/
write again: Mei rewrote the introduction after feedback.
prearrange
/ˌpriːəˈreɪndʒ/
arrange before: The meeting was prearranged by email.
Wrongly: mis-
Mis- means wrongly: a misdelivered package arrived, but at the wrong place.
Not "It went to the wrong address, so it was undelivered." — say "It went to the wrong address, so it was misdelivered.". Undelivered never arrived, and misdelivered arrived at the wrong place.
Try it: Camila: The app says my package was delivered, but it isn't here. Mateo: Then it was probably ___ to another building. Choose the word for the blank. (misdelivered / undelivered / redelivered) Answer: misdelivered — Mis- means wrongly, so a package left at the wrong building was misdelivered.
Word
Pronunciation
Example
misunderstand
/ˌmɪsʌndərˈstænd/
understand wrongly: Wei misunderstood the question and answered about prices instead.
misdeliver
/ˌmɪsdɪˈlɪvər/
deliver to the wrong place: The package was misdelivered to 12 Moffen Street.
What are the common mistakes?
Incorrect
Correct
Why
I unagree with you.
I disagree with you.
Agree takes dis-, not un-.
My essay needs work, so I have to prewrite it.
My essay needs work, so I have to rewrite it.
Re- repeats something already done, and pre- happens in advance.
It went to the wrong address, so it was undelivered.
It went to the wrong address, so it was misdelivered.
Undelivered never arrived, and misdelivered arrived at the wrong place.