## unless VS. till/until

4

I made atypo and correct the bold part above: I changed finished to finish.

Would you tell me if all the sentences are correct and whether or not they would mean the same thing?

Furthermore:

UPDATED: I am wondering we must use unless woth which of the conditional sentences?

I meant by which one of these? the firs conditional type, the second one, and so on.

2There is no need for ' next to till. Till is an older word than until and is not an abbreviation. – Matt Ellen – 2015-01-14T09:27:18.803

1

All three sentences are acceptable. Though Sentence 2 is preferred in common usage to Sentence 3, they convey the same essential meaning. I will focus on the differences between Sentences 1 and 2.

"Till" (or "until") is time-related and is roughly equivalent in meaning to "up to/ending at a (stated) point in time." In a conditional or negative statement (i.e. "not until"), it can be substituted by "(only) when/after" and implies the speaker's expectation or relative certainty that a necessary action will be performed (or a necessary event will occur) at some time in the future.

For example:

Breakfast will be served until 10:00 a.m. (unconditional, simply time-related)
The room will not be available until it has been cleaned. (negative/conditional, time-related) -->The room will (only) be available after it has been cleaned.

"Not...unless" is more "purely" conditional (not implying any relationship to time) and its meaning can be substituted by "only if." The negative element of the sentence is either expressed in the clause containing the consequence (result) or implied in the clause containing the condition (requirement). Compared with "until," the speaker is showing uncertainty that a necessary action will be performed (or a necessary event will occur).

For example:

I will not go to the party unless you do. (negative/conditional) --> I will go to the party only if you do.
I will throw away the milk unless you ask me to save it. (implied negative/conditional) --> I will throw away the milk if you do not ask me to save it.