4.3 Comparing and Contrasting

Comparing means putting two or more objects, facts or ideas together and stating in what ways they are similar or dissimilar. The two phenomena must be comparable, that is, they must have some characteristics in common.

Comparing two things is a fairly simple logical operation. Nevertheless, there is a wide variety of phrases and sentence structures that can be used to express different kinds of comparison.

In what different ways can things be compared?
􀂃 Similarity
When you want to emphasise the similarity between two things, you can use the following sentence patterns:

Some example sentences
* The characteristic feature of the totality of natural numbers, …, is logically equivalent to the principle of mathematical induction.
* A point set in S in the plane is called bounded if …. For a point set in space the definition is similar; we ….
* By way of analogy, the ALU may be thought of as a super adding-machine.
* We define an accumulation point of S in exactly the same way as we did for point set on the line.
* Sweden, like Finland, has very large resources of timber.

The following linking words and phrases may also be used to express similarity:
like …; as well as …; both … and …; just as …;
In the same way, …
Similarly, …

􀂃 Dissimilarity
Dissimilarity basically means that one phenomenon is either more or less than another in one or several respects. The following structures can be used:
(much)
(far)
(substantially)
(somewhat)
(rather)
(slightly)

Example sentence:
So even though it's non-porous, much thicker and far more reliable than gold plating, we can almost always offer our glad connectors for less than you would pay for an ordinary connector. In general, the dependence of the open-loop gain on temperature is of less importance than the thermal behaviour of the amplifier frequency response.

􀂃 Superiority and inferiority
This means saying how something is better or worse than something else, with regard to particular features. Phrases you can use include:
in a certain way
from a certain point of view
with regard to …
as regards …
in being
in that it is
inasmuch as it is
more + adjective
less + adjective
A  is  superior to/inferior to B in
giving
showing
exhibiting
more + noun
greater + noun
less + noun

Example sentences:
* The reciprocating pump is superior to the rotary pump in being more efficient.
* The yarn strength of air-vortex spun yarns is somewhat inferior to that of rotor-spun yarns, a 5% difference in strength being reported.

􀂃 Proportionality and disproportionality
When two objects, X and Y, are considered in relation to each other, the variability of certain of their features or characteristics can be compared. The comparison may produce either a proportional or a disproportional result. You can use the following sentence structures:

Example sentences:
* The higher the velocity of steam, the greater the turbine speed.
* Data input rise and fall times reduce as driver output impedance increases.
* The critical twist value, after which strength decreases, is lower for the former, but increases with increasing yarn linear density, which is the reverse of the effect found for conventional yarns.
* During expansion, the pressure varies inversely to the volume.

􀂃 Contrasting
Contrasting is a specific kind of comparison. Whereas in comparing you normally look for at least one feature that the two or more objects have in common, in contrasting you aim to identify the differences between them.
Here are some useful sentence structures:
It is  common/useful/valuable
to distinguish
to differentiate
to make a distinction
between A and B

Some common conjunctions and sentence linkers for expressing contrast:
While …, …
Whereas …, …
On the other hand, …

Example sentences:
* The RAM differs from the ROM in that it can be written into as well as read from.
* It is useful to differentiate between a blower and a liquid.
* The engine, as distinct from the earlier one, has six cylinders.
* Unlike discrete-component designs, however, the microprocessor is not programmed using …
* These differences are ascribed to the fact … most fibres have both ends spun in, whereas in the case of ring-spun yarns one fibre end frequently protrudes from the yarn.
* A hot engine will run on a weak mixture. On the other hand, a cold engine requires a richer mixture.

4.4 Defining

In science and technology, there are generally two kinds of definitions:
􀂃 the real definition, that is a definition that explains precisely the essential, intrinsic characteristics of an object.
􀂃 the nominal definition, that is one that helps to determine the meaning of a term, such as a word, sentence or symbol, e.g. in a mathematical language.

What language can I use for real definitions?
Real definitions include these functions:
􀂃 Defining an object
A  is/is equal to/equals/is equivalent to/corresponds to/is said to be/may be said to be  B = (noun with attribute)
(noun without attribute)
(noun + genitive)
(noun + preposition + object)

Example sentences:
* Geometry may be said to be a study of the properties of geometric figures.
* By a set of real numbers we mean an aggregate or class of numbers.

􀂃 Defining an object by assigning it to a category and specifying it
A  is/may be
called
termed
thought of as
referred to as
defined as

B + specification:
(relative clause)
(prepositional phrase)
(to + infinitive)
participle clause (-ing / -ed)
participle clause + to infinitive / for + gerund

Example sentences:
* A pyrometer is an instrument for measuring high temperatures.
* Milling is a machining process in which a rotary cutter equipped with a number of teeth is rotated rapidly while the work is fed under it.
* Roughly speaking, a surface is a configuration of points having a two-dimensional character.
* Brittleness may be defined as the absence of the ability to deform plastically.
* A key is the information required to locate a record within a DASD file declared with the attribute DIRECT.

What language can I use for nominal definitions?

Here are some of the sentence patterns you can use:
If A satisfies certain conditions  then it is/then it can be
said to be
called
referred to as
expressed as
expressed in the form of
termed
Z
then we call it

A defined by …/determined by …
is called
is said to be
is expressed as
is expressed in the form of
is termed
Z

Example sentences:
* A curve is called smooth if two conditions are satisfied: (1) …. (2) ….
* A function f(s) defined by f(s) = ƒ ……. is called the Laplace transform of the function f(t).
* The term computer normally refers to a general-purpose, high-speed, programmable machine that is designed to handle a wide range of computer problems.

4.5 Emphasising

In your writing you will be making statements that vary in importance. You will therefore need to make sure that the most important ones are given more emphasis than the less important ones. Details in your argument have to be presented in such a way that readers understand their relative significance.

How can I emphasise points visually?
􀂃 make use of tables, graphs, charts and other visual forms of illustration in support of your written text. It is easier for many readers to extract information from a diagram than to follow the detail of your written argument. However, you should realise that the more tables you include, the less will be the impact of each.

􀂃 visually, text that has white space around it stands out more than something that is surrounded by a lot of other text. Therefore
* make use of headings, separated from the body of writing
* occasionally break up your paragraph into bullet points. (Though this should not be overused, except perhaps in a report where it is more acceptable)

Gallium arsenide is a remarkable material with a battery of useful qualities:
􀂃 It moves electrons around three to six times faster than silicon.
􀂃 It emits light - something silicon cannot do.
􀂃 It absorbs sunlight more efficiently than silicon, making possible better solar cells
􀂃 It uses less power than silicon.

* make sure you put the main idea at the start or at the end of your paragraph so that its importance is not concealed by other sentences around it
* vary the length of your sentences, and of your paragraphs. In particular, sentences or paragraphs that are shorter than the norm do stand out.

How can I use language to emphasise points?
In spoken English, you can emphasise parts of a sentence simply by using stress on important words. In writing, of course, we cannot do this. Instead, we can emphasise particular words or phrases by putting everything into a kind of relative clause except the words we want to emphasise. These structures are called cleft sentences.

􀂃 It was …who / that …
Röntgen discovered X-Rays in 1895. (no emphasis)
It was Röntgen who discovered X-Rays in 1895. (emphasis on the person)
It was in 1895 that Röntgen discovered X-Rays. (emphasis on the date)
It was not until 1895 that Röntgen discovered X-Rays. (emphasis on the fact that it wasn't earlier than this)
It was X-Rays that Röntgen discovered in 1895. (emphasis on what Röntgen discovered)
Other cleft sentence structures:
􀂃 What … was …
􀂃 The reason why … is that …

no emphasis

Einstein showed that space-time and gravitational forces are profoundly related.
The southern hemisphere shows little response to eruptions in the north because it is dominated by oceans that damp down any change.

emphasis

What Einstein showed was that space-time and gravitational forces are profoundly related.
The reason why the southern hemisphere shows little response to eruptions in the north is that it is dominated by oceans that damp down any change.

You can draw attention to the new information that you want to present by changing the sequence of the parts of a sentence, using such structural forms as:

􀂃 One / The only … is / was …
One erasable system that is being considered by developers like IBM and 3M is a technology called magneto-optic recording.
The only time this effect has been reported was in 1995.

You can add emphasis by starting your sentence with a negative expression or one including only. Note that with these structures the subject and the main verb in the sentence have to be inverted, or changed round.

􀂃 negative expressions such as Never…, Seldom…, Rarely…; Under no circumstances…, At no time…, In no way…

no emphasis

He did not allow his assistants to be absent under any circumstances.
He had never managed to use his deductive skills so well as in this experiment.
We will know the next steps to take when the report has been carefully analysed.
Scientists have recently discovered a cure for certain types of leukemia.

emphasis

Under no circumstances did he allow his assistants to be absent.
Never had he managed to use his deductive skills so well as in this experiment
Only when the report has been carefully analysed will we know the next steps to take.
Only recently have scientists discovered a cure for certain types of leukemia.

You can also add emphasis by using balancing or parallel structures in a sentence, e.g. not only … but (also) …; just as … so …

Not only was Röntgen's discovery of X-Rays important in itself, but it led directly to the discovery of radioactivity.
Just as Avogadro saved his idea that equal volumes of gases contain equal numbers of molecules by introducing a new idea, so Kekulé rescued his idea that carbon is tetravalent by inventing the carbon-carbon bond.

Points to check in your writing
􀂃 Have I given the right degree of emphasis to my important points?
􀂃 If not, how can I highlight them better?
􀂃 Can I make more, or better, use of visual techniques to make important points stand out? e.g.
* tables, charts, graphs
* page layout
* using bullet points
* positioning ideas in paragraphs
􀂃 Do I need to change the grammatical structure of sentences to give more emphasis to important points?