Why Do I Need Future Perfect?
So you're probably wondering, 'Do I really need to use this tense? It sounds pretty specific.' It is, and you probably won't use it every day, but it will come up, and it allows you to be more specific when describing events in the future. For example, let's look at this common New Year's resolution:
I will lose weight by exercising every day.
Okay, that's all well and good, but that resolution is likely to be forgotten by mid-January. Let's try being a little more specific:
By the end of January, I will have lost ten pounds by exercising every day.
By giving a specific time, your writing is more clear (and you're probably more likely to keep your resolution). Let's take one from our simple future sentences from earlier. Earlier, we wrote:
I will finish my homework after dinner.
But what if you want to finish your homework before dinner, so you can watch TV after dinner? Use the future perfect:
I will have finished my homework before dinner.
How Do You Form Future Perfect?
While simple future uses 'will' plus the present tense form of the verb, future perfect uses 'will have' plus the past participle. So, in our first example, the future perfect verb phrase is 'will have lost' and in the second, it is 'will have finished.'
The 'will have' is pretty simple, and doesn't change, but let's talk about the past participle. For regular verbs, like 'finish,' the past participle is the same as the simple past form: the root verb with an -ed added to the end.
However, a verb like 'lose' is an irregular verb, so its simple past and past participle are 'lost.' And some irregular verbs, like 'throw' have different simple past ('threw') and past participle ('thrown') forms. Be aware of irregular verbs when using future perfect tense.