The pairs at a glance
Affect or effect Full guide →
affectverb: to influence The delay will affect the launch.
effectnoun: the result The effect was immediate.
Their, there or they’re Full guide →
theirbelonging to them Their report is ready.
therea place, or “there is” Put it over there.
they’rethey are They’re on the call.
Its or it’s Full guide →
itsbelonging to it The team changed its plan.
it’sit is, or it has It’s been a long week.
Who or whom Full guide →
whothe one doing the action Who sent the invoice?
whomthe one receiving it To whom should I send it?
Lay or lie Full guide →
layput something down (laid, laid) Lay the files on the desk.
lierest flat (lay, lain) I need to lie down.
Fewer or less Full guide →
fewerthings you count Fewer meetings this month.
lessamounts you measure Less time for each one.
Farther or further Full guide →
fartherphysical distance The office is farther than I thought.
furtherextent, or “more” Let’s discuss this further.
i.e. or e.g. Full guide →
i.e.that is: the full meaning the deadline, i.e. Friday at noon
e.g.for example: one of several a document, e.g. a report or memo
Than or then Full guide →
thancomparison This draft is shorter than the last.
thentime or sequence Check the figures, then send it.
Into or in to Full guide →
intomovement inside She walked into the meeting.
in to“in” belongs to the verb Please hand your forms in to reception.
I, me or myself Full guide →
Ithe one acting Priya and I will present.
methe one receiving Send it to Priya and me.
myselfonly when I is already in the sentence I checked it myself.
Three tests that settle most pairs
Most of the pairs above come down to one of three quick checks. Learn the checks and you can work out pairs you haven’t met before.
The substitution test Replace the word with its full form or a synonym and see if the sentence still works. “It’s ready” works as “It is ready”, so it’s. In “The team changed its plan”, “it is” makes no sense, so no apostrophe. its / it’stheir / they’reaffect / effecti.e. / e.g.
The counting test Ask whether you could put a number in front of the noun, or measure the distance. three emails → fewer emails · time can’t be counted → less time fewer / lessfarther / furthernumber / amount
The pronoun test Drop the other person, or answer the question with he or him. Send it to (Priya and) me → “to me”. Who/whom? “Him” → whom. I / me / myselfwho / whomlay / lie
Twelve more pairs for professional writing
These pairs turn up constantly in emails, reports and contracts. Each has a memory hook in the last column.
| Word | Means | Example | Memory hook |
|---|---|---|---|
| accept | to receive or agree to | We accept the terms. | accept: you agree to it |
| except | apart from | Everyone except Sam signed. | except and exclude both start ex- |
| complement | to complete or go well with | The charts complement the text. | complement completes |
| compliment | praise | Thanks for the kind compliment. | I like compliments |
| principal | main; head of a school | The principal reason is cost. | the principal is your pal |
| principle | a rule or belief | It’s a matter of principle. | principle = rule (both end in -le) |
| ensure | make certain | Please ensure the door is locked. | ensure = make sure |
| insure | protect with insurance | We insure all equipment. | insure = insurance |
| stationary | not moving | The car was stationary. | a for stand still |
| stationery | paper and envelopes | Order more stationery. | e for envelopes |
| discreet | tactful, careful | Please be discreet about this. | discreet keeps a secret |
| discrete | separate, distinct | Three discrete stages. | the t separates the e’s |
Pairs that depend on British or American English
British English sometimes uses two spellings where American English uses one: one for the noun and one for the verb, or one for each meaning. Pick one variety and keep to it in a document.
British
practice (noun) · practise (verb)Daily practice helps. Practise every day.licence (noun) · license (verb)A driving licence. Licensed to sell.programme (TV, event) · program (software)A training programme. A computer program.further for distance and degreeFurther down the road. Further details.
American
practiceDaily practice helps. Practice every day.licenseA driver’s license. Licensed to sell.programA training program. A computer program.farther for distanceFarther down the road. Further details.
Why these pairs get swapped: sound, spelling and meaning
Not every confused pair is confused for the same reason. A homophone is a word that sounds exactly like another but is spelled differently and means something else (there, their). A near-homophone sounds almost the same (accept, except). Some pairs sound different but share a meaning area (fewer, less). Knowing which kind you are facing tells you which test to use.
Homophones Same sound, different spelling Your ear can’t help, so use the substitution test: expand the word or swap in a synonym. their / there / they’reits / it’sstationary / stationeryprincipal / principle
Near-homophones Almost the same sound Say the word slowly and listen for the first syllable: ac-cept, ex-cept; af-fect, ef-fect. accept / exceptaffect / effectthan / thendiscreet / discrete
Meaning pairs Different sound, overlapping meaning Ask what kind of thing you are describing: countable or not, physical or not, subject or object. fewer / lessfarther / furtherwho / whomlay / lie
Spell-checkers catch none of the first group, because every word is spelled correctly. That is why their, there and they’re and its and it’s need a rule you carry in your head rather than a tool.
Noun or verb? Pairs that change with the job of the word
A noun names a thing (the advice); a verb names an action (to advise). Several pairs are really one word in two jobs, with a different spelling for each. Ask which job the word is doing in your sentence: if you can put “the” or “a” in front, it is a noun.
| Noun (a thing) | Verb (an action) | Example with both | Hook |
|---|---|---|---|
| advice | advise | Thanks for the advice; I’d advise waiting. | c for the thing, s for the action |
| device | devise | We devised a new device. | same pattern as advice / advise |
| practice (UK) | practise (UK) | Practise daily; practice makes progress. | US uses practice for both |
| licence (UK) | license (UK) | You need a licence; we are licensed. | US uses license for both |
| effect | affect | The change will affect sales; the effect was small. | A for action (verb), E for end result (noun) |
| loss | lose | We lose money on each sale; the loss is growing. | lose has one o and is the verb |
Affect and effect follow the same pattern most of the time: affect is the verb, effect the noun. The rare exceptions (“to effect change” means to bring it about) are covered in the full guide.
Eight pairs in one email
Confused pairs rarely appear alone. This short email uses eight of them correctly; each highlighted word has a note explaining the choice.
Subject: Office move: what changes on Monday Hi all, The move will affect¹ everyone, but its² main effect³ is more space for every team. The new building is farther⁴ from the station, so allow ten minutes more on the first day. We will have fewer⁵ desks than⁶ before, so please book one in advance. If you have questions, ask Priya or me⁷, and we will ensure⁸ you have what you need. Thanks, Daniel
- 1affect verb: the move influences everyone.
- 2its belonging to the move; “it is” would not fit.
- 3effect noun: the result, after “main”.
- 4farther physical distance you could measure.
- 5fewer desks can be counted.
- 6than a comparison with before.
- 7me drop Priya: “ask me”, not “ask I”.
- 8ensure make certain; insure would mean a policy.
Guides on commonly confused words
16 guides · newest first
Assure vs Ensure vs Insure: A Simple GuideConfused by assure, ensure, and insure? Learn the simple rule for each, with examples, a quick-reference table, and memory tricks to choose correctly.Oct 30, 2026 · 4 min read
Who vs Whom: The Rule That Actually WorksMaster who vs whom with the he-or-him substitution test, embedded clause rules, and real examples from formal to casual writing.Apr 23, 2026 · 13 min read
Lay vs Lie: Simple Rules and Real ExamplesMaster lay vs lie once and for all. The transitive-intransitive rule, every verb form, real examples, and the past tense trap that confuses everyone.Apr 23, 2026 · 13 min read
e.g. vs i.e.: How to Use These Latin Abbreviations CorrectlyLearn the exact difference between e.g. and i.e. with punctuation rules, 20+ examples, common mistakes, and a self-check exercise for professional writers.Apr 11, 2026 · 11 min read
Farther vs Further: Essential Difference GuideMaster the difference between farther and further with the physical vs figurative rule, 20+ examples, common mistakes, and a self-check exercise.Apr 11, 2026 · 11 min read
Fewer vs Less: When to Use EachMaster fewer vs less with the countable vs uncountable rule, 20+ examples, modern usage debate, and a quick test that handles every edge case in writing.Apr 11, 2026 · 9 min read
I vs Me vs Myself: Grammar GuideMaster I vs me vs myself with the drop-the-other-person test, compound subjects, prepositional phrases, reflexive pronouns, and 20+ examples.Apr 11, 2026 · 9 min read
Into vs In To: The Complete Usage Guide With 20+ ExamplesMaster the difference between 'into' and 'in to' with clear rules, 20+ examples, common mistakes, and a self-check exercise for professional writers.Apr 10, 2026 · 11 min read
Its vs It's vs Its': When to Use EachClear guide to its vs it's with substitution test, comparison tables, edge cases, and practice sentences for professional and academic writing.Apr 10, 2026 · 12 min read
Lay vs Lie: Usage Guide with ExamplesMaster lay vs lie with clear rules, present and past tense tables, 20+ example sentences, and a quick memory trick that eliminates the confusion for good.Apr 10, 2026 · 10 min read
Than vs Then: Usage Difference GuideClear guide to than vs then with comparison vs sequence rule, 20+ examples, a mnemonic that sticks, and a self-check exercise for writers of every level.Apr 10, 2026 · 8 min read
Affect vs Effect - The Simple Rule That Always WorksMaster affect vs effect with one simple rule. Clear examples, memory tricks, edge cases, and practice sentences for professional and academic writing.Mar 28, 2026 · 22 min read
Most Common Grammar Mistakes in Professional WritingExpert guide to the most common grammar mistakes in professional writing. Covers subject-verb agreement, comma splices, apostrophes, modifiers, and more with clear corrections.Mar 28, 2026 · 11 min read
Their vs There vs They're - Quick Guide with ExamplesClear guide to their, there, and they're with examples, memory tricks, and practice sentences. Covers similar homophones like your/you're and its/it's.Mar 28, 2026 · 24 min read
Who vs Whom: Clear Definitive GuideThe he-him test, working examples, and the one rule that settles every who vs whom question. Plus the cases where whom is optional even in formal writing.Mar 28, 2026 · 13 min read
Who vs Whom - When to Use Each with ExamplesLearn when to use who vs whom with the simple he/him trick. Covers formal vs informal usage, whoever vs whomever, and real examples in questions and statements.Mar 28, 2026 · 24 min read