The first conditional, also known as a Type 1 conditional or possible conditional is an English pedagogical conditional consisting of a real conditional sentence used to express a single future consequence of an action or event.
An illustrative example is "If you don't water the plant, it will die".
- If ... present simple,
Note that the order of the two parts may be changed: "I will lend it to you if I find it."
- Is the action in the past/present/future time? (either present or future)
- Does this happen once or many times? (once; in the example, the plant can't die more than once).
- Is it probable (>50%) that I won't water the plants or is it improbable (<50%). (Probable; if it is improbable we need to use a second conditional).
Note the plant dying is a good example because it obviously can't die more than once. If you use an example with something that happens repeatedly, albeit infrequently, e.g. "If I receive a pay rise, I will be happy" we start to push into the ambiguous boundaries between the first conditional and the zero conditional.
The above is how this structure is generally presented to students, however, there are potentially several complications that may arise.
The condition may be in the past; consider these two examples, which could be spoken by a teacher to a class of students:
- "If you have done your homework, you won't get a detention tomorrow."
- "If you did your homework (yesterday), you won't get a detention tomorrow."
In these cases there's a future consequence of a past action; in a class of schoolkids it's likely that most of them have done their homework, but at least a few of them haven't.
The condition may be distanced for politeness (rather than irrealis). e.g.
- If you would like a cup of tea, can you please raise your hand?
Consequence is a request
If the consequence is a request, we can use either present tense modal verbs, or past tense modal verbs to express politeness:
- If you want a cup of tea, can you please raise your hand?
- If you want a cup of tea, could you please raise your hand?
- If you want a cup of tea, would you please raise your hand?
Consequence is a demand
- If you want a cup of tea, raise your hand!
Consequence is an obligation
If the consequence is an obligation, we really need to use "must", "should" or "ought to", past tense modal verbs:
- If you want a cup of tea, you should mention it to the waiter.
- If you want a cup of tea, you must mention it to the waiter.
- If you want a cup of tea, you ought to mention it to the waiter.
- Alice speaking to Bob: "If you don't water those plants, they will die!"
- Bob, later reporting speech to Charlie: "Alice said if I didn't water those plants, they would die."
The latter sentence resembles the 2nd conditional sentence, and because of the backshifting, it's slightly ambiguous to Charlie whether Alice originally said "If you don't water those plants, they will die!" (first conditional), or "If you didn't water those plants, they would die!" (second conditional).