Grammar Quick Reference
The rules that trip people up, in plain words: why each rule exists, right and wrong examples, a memory trick, and the usual mix-ups. Where the style guides disagree, it says so.
How to use it
Type the way you'd ask a person: "its or it's", "comma before but", "who or whom", "is it lay down or lie down", "can I end a sentence with a preposition". The search knows everyday words (quotes, possessive, run on, capital letters) and forgives a typo. Tap a topic to browse instead. Each entry shows the rule first; tap Show the why, examples and trick for the rest.
Teaching with it: pick one entry a day. Read the rule, then cover the right/wrong examples and see if you can sort them, then read the why. The quiz mixes all topics; every answer links back to its entry. A link ending in #id (for example .../grammar#lie-lay) opens that entry.
Rules, style choices and myths
Not everything teachers mark is the same kind of thing. This page sorts them three ways:
- Rules of standard English that every guide agrees on (its vs it's, subject-verb agreement, no comma splices).
- Style choices where good guides disagree (the Oxford comma, numbers, capitals after a colon, "James's" vs "James'"). These have a blue Style guides differ box. Pick one and be consistent; for school, follow the guide your teacher uses.
- Myths: "rules" that were never part of English (no preposition at the end, no split infinitives, no And at the start).
The style guides, and who uses which
| Guide | Who uses it | Known for |
|---|---|---|
| AP Stylebook (Associated Press, since 1953) | Newspapers, news sites, many businesses | Saving space: no Oxford comma in simple lists, digits from 10 up, spaced em dashes, no en dashes |
| Chicago Manual of Style (University of Chicago Press, since 1906; 18th edition 2024) | Book publishers, history papers | Thoroughness: Oxford comma, words for numbers up to one hundred, unspaced em dashes |
| MLA Handbook (Modern Language Association; 9th edition 2021) | High school and college English classes | Citing sources in essays about literature; Oxford comma |
| APA (American Psychological Association; 7th edition 2019) | Psychology, science and social science papers | Citing research; digits from 10 up; Oxford comma |
Dictionaries such as Merriam-Webster describe how English is really used, including what's informal; style guides prescribe one consistent way for a publication. Both are useful, and that's why they sometimes seem to disagree.
Sources
Checked against Merriam-Webster (dictionary and usage notes), the Chicago Manual of Style (18th ed.), the AP Stylebook, the MLA Handbook (9th ed.), APA 7th ed., the Purdue Online Writing Lab, Grammarist, the Online Etymology Dictionary and Fowler's Modern English Usage; each entry lists its own. Built 2026-10-24 and reviewed for accuracy by a second reader. Works offline; nothing you type or answer leaves this device (quiz score and theme are kept in this browser only).