The aim of the precis writing should be to write sentences which satisfy two conditions, (/) it should have one definite meaning, (ii) the meaning should be clear to the readers.
“If the reader is puzzled over the exact meaning of the sentences, then the sentence is vague, if he can interpret a sentence in more than one way the sentence is ambiguous.
The causes of vagueness are many. One of the important causes is vague thinking. For example : “Motor cars are not allowed in this gateway ; any one doing so will be reported”. The writer in the second portion of the sentence confuses the motor cars with drivers so the sentence is obscure and incorrect.
Careless use of pronoun is another cause of obscurity. If a pronoun is introduced it should be clear that it is used for one definite noun. For example :
If the baby does not thrive on fresh milk, it should be boiled.
Which should be boiled—the milk or the baby? So the sentence should be rewritten as —
If the baby does not thrive on fresh milk, the milk should be boiled.
Other causes of ambiguity may be incorrect punctuation, the omission of necessary words, elipshed grammar. But the most dangerous and commonly used is wrong order of words. For example.
Wanted a nurse for a baby of twenty years.
Baby cannot be of twenty years. So the sentence should be “wanted twenty year old nurse for a baby”. Similarly there is an important difference between “The first two lessons” and ‘The two first lessons’. Language should be very clear in the case of a precis.