Lesson

Adjectives + to-infinitive -ing, that clause, wh- clauses

Complex patterns

≈ 15 min 8 block(s)

Text

Adjectives + different clause types

Some adjectives are followed by a to-infinitive, others by an -ing form (gerund), a that-clause, or a wh-clause. Knowing which structure follows an adjective helps you build correct, natural-sounding sentences in business and formal English.

  • Adjectives + to-infinitive: common with adjectives expressing readiness, willingness, or ease (e.g., ready to start, happy to help, easy to use).
  • Adjectives + -ing (gerund): used when the adjective describes a state related to an action (e.g., busy preparing, worth reading).
  • Adjectives + that-clause: often with mental-state adjectives (e.g., certain that, sure that, surprised that).
  • Adjectives + wh-clauses (or whether): used when the adjective relates to specific information (e.g., unsure whether, curious what, unclear why).

Recognize the adjective first; then choose the complement that commonly follows it.

Table

Adjective + Complement: Common Patterns

Adjective Complement type Example
easy to-infinitive The report was easy to read.
happy to-infinitive We're happy to provide additional data.
busy -ing (gerund) She is busy preparing the presentation.
worth -ing (gerund) The case study is worth reading for the team.
certain that-clause They're certain that sales will increase next quarter.
surprised that-clause We were surprised that the meeting finished early.
unsure wh-clause / whether He was unsure whether the client had signed the contract.
curious wh-clause I'm curious what the marketing team will propose.

Tip

Key rule: Match the adjective to its usual complement

There is no one-size-fits-all ending; learn common adjective patterns and use them in context.

  • Adjectives that describe willingness, readiness, or ability often take to + infinitive: 'willing to help', 'ready to sign'.
  • Adjectives that describe ongoing activity or value often take -ing: 'busy meeting clients', 'worth considering'.
  • Mental-state adjectives frequently take a that-clause: 'certain that', 'surprised that'.
  • When asking about specific information after an adjective, use a wh-clause or whether: 'unsure whether', 'curious what'.

Memorize common adjective + complement pairs and practise with professional examples.

Example

Examples in context

The team was eager to start the new project.

Our manager is busy reviewing the quarterly report.

They're certain that the contract will be renewed.

I'm curious what the stakeholders will decide.

Tip

Common mistakes to avoid

Learners often confuse patterns. Watch for these frequent errors:

  • Using to-infinitive after adjectives that need -ing: Incorrect: 'busy to prepare' → Correct: 'busy preparing'.
  • Using -ing after adjectives that require to-infinitive: Incorrect: 'happy helping' (in some contexts) → Correct: 'happy to help'.
  • Using a that-clause where a to-infinitive is standard: Incorrect: 'The task was that to complete' (nonsense) — know the pairing.
  • Using a direct question word order after an adjective: Incorrect: 'I'm curious why did she leave?' → Correct: 'I'm curious why she left.'

When unsure, check model sentences or a reliable grammar resource.

Quiz

Choose the correct sentence:

Hint: Think about the preposition that commonly follows 'interested'.

Quiz

Complete: The team was _____ the new software.

Hint: What form usually follows 'eager' to show readiness?

Quiz

Choose the sentence with correct word order and complement:

Hint: Think about how to state a belief about someone's action in a sentence.

Key Points

GrammarPoint

to-infinitive

grammar_point CEFR B1 //tuː ˈɪnfɪnɪtɪv//

the base form of a verb with 'to' (to + verb).

She is happy to help with the presentation.

GrammarPoint

gerund (-ing)

grammar_point CEFR B1 //ˈdʒɛrənd (ˈɪŋ)//

a verb form ending in -ing used as a noun or after certain adjectives (e.g., busy preparing).

The CEO is busy reviewing the contracts.

GrammarPoint

that-clause

grammar_point CEFR B2 //ðæt klɔːz//

a clause introduced by 'that' used to report facts, beliefs, or statements after adjectives.

We're certain that the shipment will arrive tomorrow.

GrammarPoint

wh-clause

grammar_point CEFR B2 //dʌbəljuː eɪt klɔːz//

a clause introduced by a question word (what, why, whether, how) used after adjectives to ask or state specific information.

The director is unsure whether the budget will be approved.

Vocabulary

eager

adjective CEFR B1 //ˈiːɡə(r)//

keen or enthusiastic to do something.

The sales team is eager to meet the new targets.

Vocabulary

busy

adjective CEFR A2 //ˈbɪzi//

occupied with activity; having a lot to do.

I'm busy preparing the quarterly presentation.