Section 4 / Lesson 3 - Describing Purpose
In this third class, we will look at another way that we can add detail to our sentences. When describing a process, there will be a reason why the steps are in a certain order. While we should not add any information that isn't in the diagram, often the reason is clear and is important for understanding the process. For example, in the frog's life cycle, the frog clearly grows lungs just before it emerges from the water as it needs them to breathe outside of the water. By adding this information, it allows us to more vocabulary and use a greater range of sentence structures. There are many different ways to show the purpose of something.
To
The first way to describe the purpose of something is all based around the word 'to':
We can use an infinitive (to + base verb) to add a reason:
The frog grows lungs to be able to breathe outside of the water.
To be able to breathe outside of the water, the frog grows lungs.
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We can also 'in order to' (a prepositional phrase), which is used in the same way as above:
The frog grows lungs in order to be able to breathe outside of the water.
In order to be able to breathe outside of the water, the frog grows lungs.
For
We can also use the word 'for' to describe why a step takes place. This is followed by a noun, most commonly a gerund (verb + ing), which turns the verb / action into a noun e.g. to breath - breathing.
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The lungs are used for breathing.
We often use it with the verb 'use', which needs the extra information added to it. How is it used? However, you can use it with different verbs too.
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The tail is grown for swimming.
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One of the best ways to use this is in a relative clause (see the last class here).
The tadpole grows a tail, which are used for swimming.
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We can also use 'for' at the end of a sentence to give the sentence.
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The tadpole grows a tail for swimming.
with the aim/purpose of
These two phrases are used the same way as the last use of 'for' above. They are put at the end of the sentence and are followed gerund. (a verb + ...ing used as a noun).
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The tadpole grows gills with the aim of being able to respire in the water.
The tadpole grows gills with the purpose of being able to respire in the water.
Note: you cannot put these after the verb to 'use'.
So that
The conjunction 'so that' links a main clause and a subordinate clause, which means that if you lose the main clause, the subordinate clause doesn't makes sense.
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The tadpole develops gills so that it can live outside of the water.
"The tadpole can live outside of the water." This is not true as they cannot breathe without lungs. This sentence must be connected to the main clause to make sense.
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Note: If you are connecting two main clauses and are showing the cause and effect between them, we use the conjunction 'so'. We will cover this more in the writing task 2 classes).
water.
