1. Lesson Overview
In this lesson, you will learn how infinitive phrases can combine sentences and simplify complex structures.
Infinitives are widely used in English to express purpose, intention, result, and planned actions. They allow writers to reduce longer clauses into more concise sentence forms.
Example:
Original sentences:
The researchers analysed the data carefully.
They wanted to discover the cause of the error.
Combined sentence:
The researchers analysed the data carefully to discover the cause of the error.
Here, the infinitive phrase to discover the cause of the error expresses the purpose of the action.
Infinitive structures are extremely common in academic writing, formal explanations, and technical descriptions because they help produce clear and efficient sentences.
By the end of this lesson, you will be able to:
-
understand how infinitive phrases combine or simplify sentences
-
recognise how infinitives express purpose, result, and intention
-
use infinitives to reduce clauses in sentence synthesis
-
identify and correct common learner errors involving infinitive structures
2. Concept Introduction
Consider the following example.
Original sentences:
The technician adjusted the device.
The technician wanted to improve its accuracy.
Combined sentence:
The technician adjusted the device to improve its accuracy.
| Structure | Example |
|---|---|
| original clause | The technician wanted to improve its accuracy |
| infinitive phrase | to improve its accuracy |
The infinitive phrase expresses the purpose of the action.
3. Core Explanation
An infinitive is the base form of a verb usually preceded by to.
Structure:
to + base verb
Example:
to analyse
to develop
to measure
to investigate
Infinitive phrases often function as modifiers that explain purpose or intention.
Example:
The scientists conducted the experiment to test the hypothesis.
Infinitives in Sentence Synthesis
Infinitive phrases allow speakers and writers to combine ideas efficiently.
Example:
Original:
The engineers designed a new system. They wanted to increase efficiency.
Combined:
The engineers designed a new system to increase efficiency.
4. Rule Table
Infinitive Structures in Sentences
| Structure | Example |
|---|---|
| verb + to-infinitive | The team decided to repeat the experiment. |
| infinitive of purpose | The scientists analysed the samples to identify the compounds. |
| adjective + infinitive | The system is easy to operate. |
| noun + infinitive | The researchers made an attempt to solve the problem. |
Infinitive Reduction
| Full Clause | Reduced Form |
|---|---|
| The scientists conducted the experiment so that they could analyse the results. | The scientists conducted the experiment to analyse the results. |
| The technician adjusted the system so that it would operate efficiently. | The technician adjusted the system to operate efficiently. |
5. Usage
Infinitives commonly express purpose, intention, and result.
1. Expressing purpose
Example:
The researchers collected additional data to verify the results.
2. Expressing intention
Example:
The company plans to develop a more efficient system.
3. Explaining results
Example:
The experiment produced unexpected results to challenge existing theories.
4. Combining ideas
Example:
The engineers modified the design to improve performance.
5. Simplifying sentences
Example:
Original:
The researchers increased the sample size so that they could obtain more accurate results.
Reduced:
The researchers increased the sample size to obtain more accurate results.
6. Signal Words
Certain verbs and expressions commonly introduce infinitive structures.
| Expression | Example |
|---|---|
| decide to | The team decided to repeat the experiment. |
| plan to | The company plans to expand its research programme. |
| attempt to | The researchers attempted to solve the problem. |
| want to | The scientist wanted to verify the results. |
| try to | The engineers tried to improve the system. |
These verbs are frequently followed by to-infinitives.
7. Special Cases
Infinitives After Adjectives
Infinitives often follow adjectives describing difficulty, ability, or readiness.
Example:
The system is difficult to maintain.
Infinitives After Nouns
Infinitives can modify nouns describing purpose or intention.
Example:
The team made an effort to complete the project on time.
8. Additional Notes
Infinitive constructions are particularly common in formal and academic writing because they allow writers to express complex ideas concisely.
Example:
The scientists designed the experiment to test the hypothesis under controlled conditions.
Such structures reduce unnecessary clauses and improve clarity and efficiency in writing.
9. Common Errors
⚠ Using gerunds instead of infinitives
Incorrect:
The researchers decided analysing the data again.
Correct:
The researchers decided to analyse the data again.
Explanation:
Certain verbs require to-infinitives.
⚠ Missing “to”
Incorrect:
The team attempted solve the problem.
Correct:
The team attempted to solve the problem.
Explanation:
Infinitive structures require to + base verb.
⚠ Incorrect verb form
Incorrect:
The scientists conducted the experiment to analysing the samples.
Correct:
The scientists conducted the experiment to analyse the samples.
Explanation:
The infinitive requires the base form of the verb.
⚠ Incorrect clause reduction
Incorrect:
The researchers increased the sample size for obtaining better results.
Correct:
The researchers increased the sample size to obtain better results.
Explanation:
Infinitives are often used to express purpose.
⚠ Ambiguous modifier
Incorrect:
The technician repaired the device to improve quickly.
Correct:
The technician repaired the device to improve its efficiency.
Explanation:
The infinitive phrase must clearly express the intended purpose.
10. Lesson Mastery
After completing this lesson, you should now be able to:
✅ understand how infinitive phrases combine or simplify sentences
✅ recognise how infinitives express purpose, result, and intention
✅ use infinitives to reduce clauses in sentence synthesis
✅ identify and correct errors involving infinitive structures