Four five seconds

How it works

How it works is a spoken pair of digits looking for a grammar. In speech, “four five seconds” can be 4.5 s (four point five), a two-digit 45 s if someone heard no point, or a rough “four, five seconds” with a comma. In writing, put the grammar back before you set a timer. 4.5 s is four seconds plus five tenths. 45 s is forty-five seconds. 4 s and 5 s are two candidate integers. 4–5 s is a range.

4.5 seconds as elapsed time is 00:00:04.5 when the last field is seconds with a tenth. It is 4,500 milliseconds. It is 4,500,000 microseconds. ISO duration form can write PT4.5S. Some parsers dislike the fraction; PT4S500ms is not standard ISO, so keep PT4.5S or an integer millisecond count of 4500 beside a unit. Do not write 4:5 and hope. 4:5 as m:ss is four minutes five seconds if you pad it to 4:05, which is 245 seconds, not 4.5.

A sports clock tenth is still a second field. 4.5 and 4.50 are the same instant if the extra zero is only display. 4.51 is not 4.5. Rounding 4.5 to 5 s is a policy, not a conversion. If a rule needs “no more than four seconds,” 4.5 fails. If it needs “at least five,” 4.5 fails the other way. The format you chose decides which rule you can even apply.

4.5 s = 4 seconds 500 milliseconds 4 s = 4.0 s, not 4.5 s 5 s = 5.0 s, not 4.5 s 45 s = ten times 4.5 s, a dropped point 4:05 as m:ss = 245 s, not 4.5 s

Four or five seconds

Four or five seconds is a choice between two integers, not a midpoint. The word “or” offers 4 s or 5 s. It does not authorise 4.5 s unless the writer said so. A delay that may fire at four seconds or at five seconds is two allowed values. A delay that fires somewhere in between is the next heading. Mixing “or” with a decimal is how a spec review argues about a half second nobody booked.

Write the choice as 4 s | 5 s, or as “4 or 5 seconds,” and keep both units. A log that prints 4 and a log that prints 5 can both be right under this wording. A log that prints 4.7 is outside the choice. If you meant “about four or five,” you meant a range and should say “to.” Format is the difference between a fork and a band.

Four to five seconds

Four to five seconds is a closed range unless you say otherwise: from 4 s up to 5 s. Inclusive writing (4–5 s, 4 to 5 seconds) usually includes the ends. If a test must fail below 4 or above 5, the band is the passing window. 4.5 s sits inside that window. 3.9 s does not. 5.1 s does not. 4.0 and 5.0 do, if the ends are included.

ISO interval form for a duration range is not a single PT string. You still write two durations, 4 s and 5 s, and name the relation: from, to, or between. A slider labelled 4–5 s is this range. A single timer set to 4.5 s is a point inside it, which is a different booking. Do not store the range as the single number 45, or as 4.5, and call the format finished.

If you can hear the “or,” you have two legal times. If you can hear the “to,” you have a band. If you can hear a point, you have 4.5. Guessing which one was spoken is not a conversion. 45 seconds is the trap when the point went missing. Four five as a digit string is 45. Four five as two spoken numbers with “seconds” after the pair is usually 4.5 in lab talk, and usually 45 in sports talk when people swallow “forty.” Ask which. Then write 4.5 s or 45 s and stop using the bare pair.