For non-native speakers of English, conditional sentences can be something of a minefield. They require study and revision and still errors will rear their ugly heads. Sadly, few native speakers of English even realise what a conditional sentence is, let alone whether they are using one or not, what type they are using and why they take the form they do.
In other words, it’s a handy thing to have a look at even if you are a native speaker, so take a look – you might be surprised. More importantly, when we fully understand the grammatical science, we can make our writing more incisive… And that’s a conditional sentence right there!
As native speakers, we are not likely to make mistakes. But to give yourself an edge, it is useful to know exactly what you are saying… and how best to say it.
There are four types of conditional sentence: Zero, First, Second, and Third. These labels are, I admit, meaningless and thus completely useless, so let’s break it down into something digestible.
A conditional sentence is a sentence that describes cause and effect. That is: a descriptive sentence that illustrates that something is done or happens, and a result follows. In its basic form, conditional sentences are a very simple concept, but, this being English, they can become convoluted and impenetrable. If I were you, I would read on…
The Zero conditional
The simplest form of the conditional sentence is the Zero form. This is the form we use to express general truths.
When the sun goes down, the sky grows dark.
If you smoke, your health suffers.
When it rains, the ground gets wet.
If I bang my head against a wall, it hurts.
Two things of note here: first, in Zero conditionals, the words ‘if’ and ‘when’ are interchangeable; second, the present simple tense is used in both clauses, the condition (when it rains) and the result (the ground gets wet).
A common error in the use of Zero conditionals is the use of the future tense in the result clause: “When it rains, the ground will get wet.” This is incorrect. This is the form used in the First conditional and it changes the meaning slightly.
The First conditional
First conditional sentences are used to describe situations that are logical, even likely, but not necessarily certain.
If you come to my party, I’ll be very happy.
If you work hard, you will succeed.
If I get there on time, I’ll buy the first drink.
If I bang my head against a wall, I’ll break my skull.
Because there is an element of uncertainty in these causes and results, the word ‘when’ cannot be used in the conditional clause (although ‘should’ is possible). The result clause uses the future simple (will).
Whereas the Zero conditional expresses causes and results that are always true, the First conditional usually refers to an event in the future and its likely outcome.
The Second conditional
Second conditional sentences describe unrealistic or unlikely conditions and their likely (but by definition, unrealistic) results.
If I won the lottery, I would retire.
If I had a car, I would drive you wherever you wanted to go.
If I met George Clooney, I could ask him why he made those Nescafé adverts.
If I banged my head against a wall, I might demolish it.
Second conditionals express ‘unreality’ by using the past simple tense to describe present or future events in the conditional clause, and the results are described with modal verbs such as ‘would’, ‘could’, ‘should’, or ‘might’.
The Third conditional
Third conditionals describe the impossible. They are ‘what if’ causes and effects. If the past could be changed, then the results would have been different.
If I hadn’t missed the bus, I would have been on time.
If I had seen you, I would have waved.
If I’d known you needed a lift, I could have picked you up.
If I’d banged my head against the wall, you would have thought I was stupid.
Third conditionals express impossibility by describing simple past (conditional) events using the past perfect tense (usually used for past events that happened before another past event). The results are described using modals such as ‘would’, ‘could’, and ‘might’ and the present perfect. It isn’t possible, but if I could go back in time and do something differently, the result would also have been different.
Exceptions and oddities
There are occasions when the future tense can be used in First conditional sentences. This is when the conditional clause will take place after the result clause.
If cleaning the house will make you happy, then I’ll do it.
If paracetamol will bring down my temperature, I will take some.
The phrase ‘were to’ can be used in Second conditionals to express highly undesirable or unthinkable causes.
If I were to miss another day of work, I’d get the sack.
If I were to get sick again, I don’t know what I’d do.
If the rent were to be higher, I wouldn’t be able to afford it.
Notice how, even though the first person singular is being used (I) the word ‘were’ is still used (not ‘was’). This is an odd, archaic usage known as the past subjunctive and it is only used in conditional sentences these days – and even then, less frequently all the time.
Once the phrase ‘If I were you, I’d do it differently’ was commonplace, but these days, the usual first person conjugation is used (If I was you, I’d do it differently).
If the conditional clause comes first, it is separated from the result clause with a comma.
The result clause isn’t separated by a comma if it comes before the conditional clause.