Please explain to me "unless" and "if"

[Mlngvt]

Dear teachers,
Please explain to me "unless" and "if".
Please give an example for each.
Thanks

[Alan]

Hi mlngvt,

Unless has the sense of if not. Look at these sentences:

If you hurry, you'll catch the train.

If you don't hurry, you'll miss the train.
Unless you hurry, you'll miss the train.

Alan
_________________
English as a Second Language
You can read my ESL story Present Simple

[Mlngvt]

Thanks teacher for your reply.
Please have a look at my practice:
1. Is this sentence right if the word "up" will be omitted?
2. Is this sentence wrong if the word "up" won't be omitted?.
I will replace sentence 2 like this:
3. Is this sentence wrong unless the word "up" will be omitted?.

She still does the washing up by hand because she is too poor to buy a washing machine.

Thanks.

[Conchita]

She still does the washing up by hand because she is too poor to buy a washing machine.

[Mlngvt]

Thanks Conchita for your correction. It's very useful to me.
Is the original sentence or the sentence after omitting 'up" right?
Please make it clear. Thanks.

[Conchita]

I suggest you write either:

She still does the washing up by hand because she is too poor to buy a dishwasher.

Or:

She still does the washing by hand because she is too poor to buy a washing machine.