a / an / theDo I need a, an, or the here?active / passiveWhen should the affected thing become the subject?affect / effectAffect or effect?am / is / areWhen do I use am, is, or are?child / childrenWhen does a count noun need a plural form?despite / althoughCan despite introduce a full clause?did + base verbDid you go or did you went?do / doesWhy does she work have -s but I work does not?does + base verbWhy is it does she work, not does she works?each / everyEach or every?-er / more ... thanHow do I compare two things?few / a fewFew or a few?if + present, willIf it rains, will we leave?if I knew / had knownIf I knew or if I had known?imply / inferWho implies and who infers?less / fewerLess or fewer?make / doMake or do?may suggest / provesDoes may suggest mean prove?much / manyMuch information or many information?must not / do not have toMust not or do not have to?past simple / present perfectI went or I have gone: does the time matter?rarely + inversionWhy is it rarely had they seen?respectivelyWhat does respectively pair?said / reported tenseMust every tense move back in reported speech?say / tellWhen do I use say or tell?since / forSince or for with time?that / whichCan I use that after a comma?used to / be used toUsed to do or be used to doing?who / whomWhen is whom used in formal English?will / going toWill or going to for a plan?work / workingI work or I am working: which fits now?some / anyHow do I choose some or any?there is / there areHow do I say something exists somewhere?my / mineWhat is the difference between my and mine?open / do not openHow do I give a short instruction?was / were + -ingHow do I describe an activity in progress in the past?have to / mustShould I use have to or must for obligation?at / on / inAt, on or in for time?-ing / to + verbShould the next verb take -ing or to?have been + -ingWhen do I use have been doing?enough / tooHow do I express sufficient or excessive degree?the / zero articleWhen is no article needed?who / which / that / ØWhen can I omit a relative pronoun?although / howeverCan although and however be swapped?wish / if onlyHow do I express a wish contrary to fact?used to / wouldCan would describe a past habit?its / it’sWhat is the difference between its and it’s?comma / semicolonCan a comma alone join two independent clauses?parallel structureHow do I keep a list grammatically parallel?noun / verbCan nominalisation obscure a sentence?not all / noneDo not all and none mean the same thing?even / still / stopCan wording presuppose an unstated fact?it is ... thatWhat does It was ... that focus?onlyHow does only change meaning by position?because / because ofWhat follows because and because of?indirect questionsWhy does an indirect question use statement order?either / neitherHow do either and neither refer to two alternatives?unless / if notCan unless always replace if not?during / whileWhat follows during and while?like / asHow do like and as differ in comparisons and roles?stop doing / stop to doWhy do stop doing and stop to do mean different things?remember doing / remember to doWhat is the difference between remember doing and remember to do?suggest + -ing / that-clauseCan suggest take a person plus to-infinitive?needn’t / mustn’tWhy do needn’t and mustn’t differ?whether / ifWhen are whether and if not interchangeable?must have / might have / can’t haveHow do modal perfect forms express past deductions?question tagsHow do question tags choose their auxiliary and pronoun?as long as / ifWhat does as long as add to a condition?