Non finite clauses functions

To-infinitivals

To-infinitivals appear in many constructions, functioning as complements or adjuncts

#	Function	Example	Notes
1	Subject	To turn back now would be a mistake.	Non-finite clause functions as subject.
2	Extraposed subject	It would be a mistake to turn back now.	Preferred alternative to subject infinitival.
3	Extraposed object	We considered it sensible to take legal advice.	The infinitival is extraposed; it is anticipatory object.
4	Complement in VP	I hope to convince them of my innocence.	Complement licensed by the verb.
5	Complement in PP	We acted in order to keep fit.	Infinitival complements the preposition order within the PP in order to….
6	Adjunct in clause	I go to the gym to keep fit.	Purpose adjunct.
7	Complement in nominal	It provides an opportunity to broaden the mind.	Infinitival complements the noun opportunity.
8	Modifier in nominal	We found a big box in which to keep them.	Relative construction modifying box.
9	Modifier in nominal	We found a big box to keep them in.	Infinitival modifier with stranded preposition.
10	Complement in AdjP	He was anxious to make a good impression.	Complement licensed by the adjective.
11	Indirect complement	The twins are still too young to be left alone.	Licensed indirectly by the degree construction (too…to).

Infinitival interrogative clauses

Infinitivals functioning as complements in VPs, PPs, nominals, and AdjPs can be interrogative– though only if the head licenses one, of course.

#	Function	Example	Notes
1	Complement in VP	I don’t know whether to accept their offer.	Complement licensed by the verb know.
2	Complement in AdjP	I’m not sure how to proceed.	Complement licensed by the adjective sure.
3	Complement in PP	They can’t agree on what to do about it.	Complement of the preposition on.
4	Complement in nominal	A decision whether to go ahead hasn’t been made.	Complement licensed by the noun decision.

Bare infinitival

In contrast to to-infinitivals, with their wide range of uses, bare infinitival clauses occur in only a very limited set of functions.

They are almost entirely limited to being (internal complements licensed by certain verbs*, most often modal auxiliaries or the dummy auxiliary “do”, with no subject permitted.

Function	Example	Notes
Complement licensed by a modal auxiliary	You must take legal advice.	All modal auxiliaries license a bare infinitival complement.
Complement licensed by auxiliary do	They didn’t tell us. / Do be careful.	Auxiliary do takes a bare infinitival complement.
Complement licensed by help	She helped me carry the boxes.	Help licenses either a bare infinitival or a to-infinitival (help me to carry).
Complement licensed by make, let, see, etc.	They made him apologise. / She let us leave. / I saw him cross the road.	Certain causative and perception verbs license a bare infinitival.
Complement licensed by specifying be	Why be so pessimistic? / All I did was be honest.	Bare be appears in a few special constructions, including specifying be.

Gerund participle

The range of functions in which gerund-participial clauses are found is broadly comparable to that of to-infinitivals, but there are some important differences.

Function	Example	Notes
Subject	Bringing him in on the deal was a great idea.	Gerund-participial clause functions as subject.
Extraposed subject	It’s been a pleasure talking to you both.	Extraposed subject after anticipatory it.
Object	I find supervising Max rather stressful.	Gerund-participial clause functions as direct object.
Extraposed object	He considers it a waste of time going to meetings.	The gerund-participial is extraposed; it is anticipatory object.
Complement in VP	I didn’t bother answering their letter.	Complement licensed by the verb.
Complement in PP	He insists on checking everything himself.	Complement of the preposition on.
Supplement in clause	Having read the paper, I can’t see why you care.	Supplement expressing prior circumstance (perfect gerund-participial).
Modifier in nominal	Who was the doctor performing the operation?	Gerund-participial clause modifies the noun doctor.

Past participles

Past-participial clauses have a quite limited distribution. They are pretty much restricted to the three functions shown (two complements considered one actually)

Function	Example	Notes
Complement in VP	She has written another novel.	Past participle forms part of the perfect construction with auxiliary have.
Complement in VP (complex catenative construction)	I could have you dismissed on the spot.	Past-participial clause is licensed by have in a causative construction.
Modifier in nominal	The guns stolen in the break-in were recovered.	Past-participial clause modifies the noun guns.
Supplement	Brought up in Glasgow, he emigrated to L.A.	Supplementary past-participial clause expressing background circumstance.