“Unless / in case / as long as”

Besides if, English has several other linking words for conditions, each with its own meaning.

💡Just like if, all of these take a present tense for the future, not will: in case it rains (not: in case it will rain), unless you come (not: unless you will come).

Unless already carries the negative idea (“if not”, “except if”), so the verb after it is usually positive.

• Unless we leave now, we'll be late.

  = If we don't leave now…

• I won't call you unless there's a problem.

• Don't touch that unless you know what you're doing.

• Do you need a coat? — Not unless it gets really cold.

• Unless is used when the condition is the only exception. Some if … not sentences can't be changed to unless, especially when you talk about feelings about something not happening: I'll be upset if you don't come (not: unless you come).
• Questions normally use if, not unless: What will you do if you don't pass?

In case gives the reason for doing something now: to be ready for something that might happen later.

• Save the file now in case the computer crashes.

• Take a photo of your passport in case you lose it.

In case is not the same as if. Compare:

• I'll cook extra rice in case your friends come.

  I cook now, whether they come or not

• I'll cook extra rice if your friends come.

  I cook only if they come

• just in case = for a smaller possibility: I don't think we'll need it, but I'll bring a charger just in case.
• in case + past explains something you did: I gave her my number in case she needed help.
• in case of + noun = if there is (common on signs and instructions): In case of fire, use the stairs.
• In American English, in case is sometimes used almost like if: In case you need me, I'm in my office. When learning, keep the two meanings separate as above.

These give a strict condition: the result happens only if this condition is met. As long as / so long as are common in speech; provided (that) / providing (that) are more formal and common in rules and contracts.

• You can borrow my laptop as long as you're careful with it.

• As long as you practise every day, your speaking will improve.

• Guests may use the pool provided that they shower first.

• I'll lend you the money, providing you pay me back next month.

💡As long as can also be about time, “for the whole time that”: You can stay as long as you like. Read the whole sentence to see whether it is a condition or a length of time.

Even if says the result stays the same whether or not the condition happens. Don't confuse it with even though, which talks about a fact (see the lesson “Although / though / despite”).

• I'm going to the beach even if it rains.

  we don't know yet if it will rain

• Even if we leave now, we won't get there on time.

• Even though it was raining, we went to the beach.

  it really was raining

• ✗Unless you don't study, you will fail the test.

  ✓Unless you study, you will fail the test. / If you don't study, you will fail the test.

  Unless already contains the negative.

• ✗Bring a jacket in case it will get cold.

  ✓Bring a jacket in case it gets cold.

  Use the present after in case for the future.

• ✗I won't go unless you will come with me.

  ✓I won't go unless you come with me.

  No will after unless.

• ✗Take an umbrella in case of it rains.

  ✓Take an umbrella in case it rains. / … in case of rain.

  In case + clause; in case of + noun.

• ✗Even it rains, we'll play football.

  ✓Even if it rains, we'll play football.

  You need even if, not even alone.

• ✗Even though it rains tomorrow, I'll go.

  ✓Even if it rains tomorrow, I'll go.

  We don't know if it will rain → even if.