|1. Infinitives as Subject (To practise is important / It's important to practise)|
In old English, infinitive clause can function as the subject of a sentence.
To get a good job is ideal.
To study diligently is important.
To drink plenty of water is good for the body.
|However in modern English, this is not common. The usual form is to use "it" to introduce a subject and place the infinitive clause after.|
It's ideal to get a good job.
It's important to study diligently.
It's good for the body to drink plenty of water.
|The -ing form is also possible to use to begin a sentence.|
Driving a truck is not easy.
Traveling by plane is convenient.
Speaking in public is always nerve-racking.
|2. Infinitives as Subject Complements|
Infinitive clause can be used after "be" as a subject complement.
Her dream is to become a famous ballerina one day.
You job is to get the clients to sign the contract today.
You are to inspect the condition of the plane thoroughly.
|3. Infinitives as Object Complements|
Infinitive clause can be used as object of verbs.
She likes to sing when she's driving.
Walter enjoy to travel abroad by himself.
I prefer to shower in the morning before work.