For or Since: What Is the Difference?

For or Since: What Is the Difference?

Have you ever wondered how to talk about an event that began in the past and continues into the present?

In English, we often use prepositions to place a noun, pronoun or noun phrase in time. This way, we can communicate the passage of time.

One common problem that English learners face is how to use prepositions of time. Two of the most common prepositions of time are for and since.

English learners often have difficulties with these two prepositions, because their native languages may use prepositions differently. 

Consider the following sentences:

I've been travelling for three years.

I've been travelling since 2012.

Today, you will learn about why you should use for in the first sentence, and since in the second sentence.

For

In English, we use the preposition for to talk about an amount of time or space. The amount of time could be seconds, minutes, hours, days, months or even years.

The amount of time does not need to be exact. You could use for when you are talking about vague periods of time, like "for the weekend", "for ages" or "for a long time".

The important point is that for is used to specify¹ a period of time.

In English, the basic formula for using for is this:

for + a period of time

For can be used when talking about the past, present or future.

Here are three example sentences that use similar vocabulary, but use different verb tenses.

(Past) Last year, I traveled for three weeks.

(Present Continuous) I'm travelling for three weeks.

(Future) Next year, I will travel for three weeks.

Regardless of the verb tense, the preposition for is still followed by a period of time.

"For" in popular music

You can hear examples of "for + a period of time" in many songs.

For example, in the popular movie “Frozen”, the character Anna sings,

You heard the singer say "for years." She says "for" because the word "years" refers to a period of time. The prepositional phrase "for years" tells how long the singer has roamed the empty halls.

Since

In English, we use since to refer to a point of time. Since can refer to a point after a specific time or event in the past. Or it can refer to a particular point beginning sometime in the past and continuing until the present time. The particular point in time could be anything – last Tuesday, 2008 or midnight, for example.

The important point is that since is used with a particular point in time.

The basic formula for using since is this:

since + a particular point in time.

In sentences with since, we usually use perfect tenses. When using since, we normally use present perfect and past perfect tenses in the main clause of the sentence. You wouldn't use since when you are talking about the future because, by definition, since refers to specific point in the past.

Here are two examples in the present perfect tense:

It has been raining since 8 a.m.

I have been walking since 10 p.m.  

"Since" in popular music

You can hear the word since in many popular songs. Here is the group "The Temptations" using the preposition since in "Since I Lost My Baby".

Since I lost my baby

Since I lost my baby

Since I lost my baby.

In the song, since is followed by "I lost my baby." This means that the singer lost someone he loves. Because he lost the person he loves at a specific point in time, you use the preposition since.

For vs. Since

Remember, for is used with a period of time.

Since is used to refer to a specific point in time.

You can use for and since with similar verb tenses, if you wish. Here are two examples: 

I have been walking for five hours.

I have been walking since 10 p.m.

We have lived here for 20 years.

We have lived here since 1985.

In the example sentences, both for and since show an event that began in the past and continues into the present.

But please remember this: for can be used with other verb tenses, including the future!

I hope that you remember this lesson for a long time!

Words in This Story

vague – adj. not clear in meaning : stated in a way that is general and not specific

formula – n. a plan or method for doing, making, or achieving something

roam – v. to go to different places without having a particular purpose or plan

1 specify   

vt.指定，详细说明

参考例句：

• We should specify a time and a place for the meeting.我们应指定会议的时间和地点。
• Please specify what you will do.请你详述一下你将做什么。