Dictionary & file formats
Knowledge Base
Plain explanations of the spelling, grammar, and punctuation rules a spell checker highlights, and of the document formats you can check.
Dictionary
The spelling, grammar, and punctuation terms behind the mistakes a spell checker flags, each with examples.
- How to Use Apostrophes The apostrophe has two jobs: it marks letters left out, as in don't, and it shows possession, as in the cat's bowl. Making a word plural is not one of them.
- What Is a Comma Splice? A comma splice joins two complete sentences with nothing but a comma. There are four simple ways to fix one, and one word to watch: however.
- What Is a Dangling Modifier? A dangling modifier is a phrase with nothing in the sentence to describe, so it attaches itself to the wrong thing: walking to work, the rain started. Every word is right, and the sentence is still wrong.
- What Is a Homophone? Homophones sound the same but differ in spelling and meaning, like there, their and they're. Every one of them is a real word, which is why a plain spelling check lets them through.
- What Is the Oxford Comma? The Oxford comma is the last comma in a list of three or more, the one before the final and: red, white, and blue. Using it is a matter of style; using it consistently is not.
- What Is the Passive Voice? In the passive voice the subject receives the action instead of doing it: the report was written by Sam. It is not a grammar mistake, but it can hide who did what.
- What Is Proofreading? Proofreading is the last careful read of a finished text, looking for mistakes in spelling, grammar, punctuation and consistency before anyone else sees them.
- What Is a Run-On Sentence? A run-on sentence runs two or more complete sentences together without the punctuation or joining word they need. It is about structure, not length: a long sentence can be perfectly correct.
- American and British Spelling Color or colour, organize or organise, traveled or travelled: many English words have more than one correct spelling. The rule that matters is to pick one variety and keep to it.
- What Is Subject-Verb Agreement? A verb has to agree with its subject in number: one dog barks, two dogs bark. The rule is simple; the subjects that hide from it are what make it hard.
File formats
The document formats the spell checker can open, what is inside each one, and what happens to it when you check it.
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DOCX - Microsoft Word Document
.docxDOCX is the format Microsoft Word has saved documents in since Word 2007: a ZIP package of XML files, standardised as Office Open XML. -
MD - Markdown
.mdMarkdown is plain text with a light set of symbols for formatting: hash signs for headings, asterisks for emphasis, hyphens for lists. It reads well as it is and converts cleanly to HTML. -
ODT - OpenDocument Text
.odtODT is the text document format of the OpenDocument standard: the default in LibreOffice Writer, an ISO standard, and open to any program that wants to read or write it. -
PDF - Portable Document Format
.pdfPDF fixes a document's layout so it looks the same on every screen and every printer. It is made for reading and printing, which is exactly why editing the text inside one is hard. -
RTF - Rich Text Format
.rtfRTF is a document format Microsoft created in 1987 so formatted text could move between word processors. It is plain text underneath, with the formatting written as control words. -
TXT - Plain Text File
.txtA TXT file holds nothing but characters: no fonts, no bold, no pictures. That makes it the simplest document format there is, and the one every device can open.