23강 / Concept 023 / 의문사 + to부정사, to부정사의 부정

Summary

The lesson covers two extensions of the noun use of the to-infinitive: question word + to-infinitive and negating a to-infinitive.

Question word + to-infinitive

A question word followed by a to-infinitive forms a unit with a noun-like meaning. It can appear in different parts of a sentence, such as the subject, complement, or object. The lesson emphasizes recognizing the construction rather than identifying its exact grammatical role.

Common forms include:

• what to do — what to do
• when to start — when to start
• where to go — where to go
• how to use it — how to use it or the way to use it

Choose the question word that fits the intended meaning. How to often refers to a method.

Rewriting the construction

A question word + to-infinitive can often be rewritten as question word + subject + should + base verb, with essentially the same meaning. The subject is supplied by context.

• I don’t know what to do. → I don’t know what I should do.
• Please tell me when to start. → Please tell me when I should start.

Common phrases include what to eat, what to wear, and how to use it.

Negating a to-infinitive

To make a to-infinitive negative, place not immediately before to:

not to + verb

The negation applies to the infinitive, not to the main verb.

• Mom told me not to help my younger sister.
• He promised not to smoke again.
• I woke up early not to miss the train.

The lesson also notes that placing not before other non-finite verb forms, such as gerunds and participles, is a related pattern covered elsewhere.

Practice and lesson focus

The exercises ask students to complete sentences with an appropriate question word + to-infinitive, rewrite sentences using the equivalent question word + subject + should + verb construction, and form negative infinitives by placing not before to.

The central advice is to recognize these expressions as units, choose the question word that fits the meaning, and remember that not goes directly before to when negating an infinitive.

Speakers and source

• Teacher Jeong-o — instructor presenting the grammar lesson.
• Middle School English TV — channel/source identified in the opening.