1. Ask the Key Question:

Direct Object (DO):

“Subject + Verb + What/Whom?”

If the infinitive answers this, it’s a direct object.

Example: “She loves to sing.”

“Loves what?” → “to sing” (Direct Object).

Adverbial Infinitive:

“Subject + Verb + Why/How/When/Where?”

If the infinitive answers this, it’s adverbial.

Example:
“She exercises to relax.”

“Exercises why?” → “to relax” (adverbial).

3. Try the “In Order To” Test:

If you can replace the infinitive with “in order to”, it’s adverbial:

“He studies to pass.” → “He studies “in order” to pass.” (Adverbial).

If not, it’s likely a direct object:

“She wants to sleep.” → ❌ “She wants “in order” to sleep.” (Makes no sense → Direct Object).

4. Examples to Compare:
Sentence Test Question Answer Function
“She is learning to swim.” “Learning what?” “to swim” Direct Object
“He is shouting to help.” “Shouting why?” “to help” Adverbial
“They hate to wait.” “Hate what?” “to wait” Direct Object
“She naps to recover.” “Naps why?” “to recover” Adverbial

“She wants [to travel the world].”

“Wants what?” → “to travel the world” (DO).

“They hate [to wake up early].”

“Hate what?” → “to wake up early” (DO).

“He attempted [to climb the mountain].”

“Attempted what?” → “to climb the mountain” (DO).

“I wish to buy a car”

“She kills to feed her anger”?

why does she kill? to feed her anger. (adverbial)

“She trains to become the best”