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Which one to use?Intermediateconjunctionpreposition
So thatvsIn order to
'So that' introduces a purpose clause with its own subject; 'in order to' introduces a purpose infinitive with the same subject.
Side-by-side comparison
So that
conjunction"So that" introduces a full clause with subject and verb to explain purpose: "I saved money so that I could travel". It needs an explicit subject.
She wrote down the directions so that she would not forget them on the way.
He turned the music down so that his flatmates could sleep properly.
Please be quiet so that everyone can hear the instructions clearly.
In order to
preposition"In order to" and "to" alone introduce an infinitive when the subject is the same: "I saved money to travel". They are simpler and more direct.
She saved money every month in order to buy a laptop for university.
He practises English every day to improve his chances of getting the job.
They left home early in order to avoid the morning traffic on the motorway.
Common mistake
- •The classic error: using TO when subjects are different.
- •"I sent the report early to the client could review it" is wrong (different subjects: I sent / the client reviews), use SO THAT: "I sent the report early SO THAT the client could review it." With the same subject, the infinitive is more concise: "She works hard TO achieve her goals" (more natural than "so that she can achieve").
Trick to remember it
- •Subject test: are the two subjects (main clause and purpose clause) the SAME or DIFFERENT? Same subject = TO / IN ORDER TO + infinitive.
- •Different subject = SO THAT + clause with modal (can/could/will/would).
- •The presence of a modal in the purpose clause is the key signal that SO THAT is needed.
Quick rule
"To / in order to" = purpose with same subject (+ infinitive): "She studies to pass." "So that" = purpose with different subject (+ clause with modal): "She explains clearly so that students can understand."
Did you know?
Purpose clauses are one of the domains where Spanish and English diverge in a systematic and elegant way. Spanish uses: "para + infinitivo" (same subject) vs "para que + subjuntivo" (different subject). English has the exact same logical distinction but expresses it differently: "to/in order to + infinitive" (same subject) vs "so that + clause with modal" (different subject). What Spanish expresses with the subjunctive ("para que pueda," "para que sepa"), English expresses with modals ("so that he can," "so that she knows"). This functional correspondence. Spanish subjunctive = English modal in purpose clauses, is one of the most elegant grammatical equivalences between the two languages.
Practise what you learned
Exercise 1 · Pick the right one
She saved money _____ buy a new laptop.
Exercise 2 · Pick the right one
He whispered _____ not wake the baby.
Exercise 3 · Form the word
Related word pairs
For + -ingvsTo + infinitive
To express purpose: 'for' is followed by a noun or gerund; 'to' is followed by an infinitive.
GerundvsInfinitive
Some verbs take a gerund (-ing), others take an infinitive (to + verb), and some take both with different meanings.
Zero conditionalvsFirst conditional
'Zero conditional' expresses general truths (if + present); 'first conditional' expresses possible future situations.
AvsAn
'A' is used before consonant sounds; 'an' is used before vowel sounds.
Bryan López
Founder of SpeakUP Academy