These questions ask what kind of time relation a sentence expresses: length, starting point, deadline, continuation or an outer limit. Identify that meaning first, then inspect the grammar of the words that follow.
Match meaning and grammar
For answers how long: they practised for forty minutes. Since names when an unfinished period began: she has lived here since April. By sets the latest time for a completed act: send the form by Thursday. Until describes an action or state continuing to an endpoint: wait until Thursday. Till has the same endpoint meaning and is an informal correct form.
| Signal | Choice and example |
|---|---|
| Measured length of time | Use for: for five months. |
| Starting point of a period still continuing | Use since: since last spring. |
| One-off completion no later than a stated point | Use by: finish the repairs by noon. |
| Action or state continuing to an endpoint | Use until or till: remain outside until dusk. |
| A noun phrase naming an event or period | Use during: during the exhibition. |
| A clause with its own subject and verb | Use while: while the children slept. |
| A period measured backward from now | Put ago after the period: several weeks ago. |
| A bounded span with two endpoints | Use from with to or until: from March to June, from dawn until noon. |
| An exact point counted forward versus a maximum limit | Use in for the future point and within for any time before the limit: in four days, within four days. |
Common traps
| Tempting route | How to reject it |
|---|---|
| Using since with a measured length or for with a starting date | Ask how long or since when. A duration takes for; the point where an unfinished period began takes since. |
| Swapping by and until | A completed act needs a deadline marked by by. A state or activity that continues needs an endpoint marked by until or till. |
| Putting while before a noun phrase | Look for a subject and verb after the gap. Without that clause structure, use during before the event noun phrase. |
| Starting a bounded span with since | Two stated endpoints need the paired frame from with to or until. Since does not pair with to. |
| Treating in and within as interchangeable | In points to a time measured forward from now. Within sets a ceiling and allows an earlier completion. |
Try it
Select all that apply: which sentences correctly match completion with by or continuation with until?
- The inspector will complete the audit until noon.
- The inspector will complete the audit by noon.
- The inspector will remain on duty until noon.
- The inspector will remain on duty by noon.
Complete with the marker while followed by the exact words she was speaking: ___, the audience remained silent.
Which sentence uses the standard word order to locate an event two years before now?
- We moved here ago two years.
- We moved here for two years ago.
- We moved here before two years.
- We moved here two years ago.