So, you have the spelling checker turned on in your word processor, or you run a spelling checker against your text. All's well, right?
Not necessarily. A significant number of words are homophones—they sound alike, or almost alike, but have different meanings. A spelling checker merely verifies that they are words in its dictionary.Let's look at some sentences that a spelling checker would not report about, and see what might be wrong with them.
Here are the words that were misused:
Alan Cooper's Homonyms page offers a very long list of sound-alike words.
Poor grammar and typographical errors cause confusion and mistrust—the reader doesn't trust the information and so gives up.
Another category of problems that a spelling checker will not catch involves grammar, idioms, and omissions. Take a look at these sentences.
In sentence 1, a word seems to be missing. Perhaps the sentence should begin "Back then, none of my friends knew". In any case, "leave alone" is not grammatical—it should be "let alone".
Sentence 2 might have originally had the phrase "one of the world's most expensive big cities". Maybe the author then decided to be more specific and make it "fifth", but then should have recast it as "the world's fifth most expensive big city".
Sentence 3 uses "ravishing" to describe "malls". That adjective is normally used to describe persons, not buildings. I'd query the author to make sure I understood his intent.
In sentence 4, the phrase "enjoys his work to be edited" is not grammatical. It could be expressed as "likes his work to be edited" or "likes having his work edited" or "enjoys having his work edited" but "likes" and "enjoys" are not aways interchangeable. Some verbs pair with gerunds (-ing forms) and some with infinitives (to forms) but very few can take either. "I like to swim" is idiomatic, as are "I like swimming" and "I enjoy swimming" but "I enjoy to swim" is not. Here is a good page that discusses the matter of verbs and whether they take gerunds or infinitives.
Sentence 5 begins with a verb ("train") whose direct object is plural ("mind and eyes"). Next we see an adverbial phrase about HOW to train: "in a manner that ...". But then the sentence continues with a singular pronoun ("it") that refers back to the object, which is plural, so the pronoun must be "they". Perhaps the author just matched the number of the pronoun with the nearest preceding noun, but it's not the manner that is able; rather it is the mind and eyes that are able.
Sentences 6 and 7 are instances of a common error non-native speakers make -- using "refer" without "to". You would ask someone to rectify the errors by referring to your handwritten copy, and you could run the application, refer to the test cases, etc. Alternatives would be to use the phrases "rectify the errors by consulting" and "consult the test cases".