Explaining the Difference: "For" and "Since"

The differences between "for" and "since" are often subtle. To help clear up any confusion students may experience when using these two words, this article will take a close look at each and offer tips on how to present them in your lessons.

Expressing Periods of Time

The prepositions "for" and "since" are used to express periods of time.

"Since" combined with a specific point in the past indicates when a period of time began, such as in the following examples:

• since Monday
• since last year
• since 1989
• since then
• since it began
• since childhood
• since we last met

On the other hand, "for" is used in combination with a length of time to express how long something has existed or has been happening.

• for 20 years
• for a while
• for a long time
• for one hour
• for decades
• for a few months

You can demonstrate the differences in nuance to your students by comparing the two responses to this "how long" question.

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The first response refers to the starting point only, but the second expresses the duration of time, from the start until the present.

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Because it refers to a starting point, "since" is used in the perfect tense.

I've been at the airport since noon.

"For," however, can be used to talk about any time. Try asking your student if they can change the previous example to refer to a past, present or future situation. 

I was at the airport for three hours.

I've been at the airport for three hours.

I'll be at the airport for three hours.

Explaining a Reason or Cause

It's common to use "because" when giving a reason, and it can come at the beginning or in the middle of a sentence. "For" and "since" can be used in the same way.

I prefer eating out because I'm too lazy to cook.

Because I'm too lazy to cook, I prefer eating out.

Explaining reasons using “since”

Although it can go at the beginning or in the middle of a sentence, "because" is often used in the middle in daily conversations. "Since," however, is common in both positions. It also sounds a little more casual than "because."

I prefer to eat out since I'm too lazy to cook.

Since I'm too lazy to cook, I prefer to eat out. 

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We decided to go to the park since the weather was nice.

Since the weather was nice, we decided to go to the park.

Explaining reasons using “for”

"For" can be used just like the other two, but it sounds uncommonly formal.

For I'm too lazy to cook, I prefer to eat out.

I prefer to eat out, for I'm too lazy to cook.

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For he is a good person, he's blessed with many friends.

He's blessed with many friends, for he is a good person.

Be sure to point out that while they may read it in a classic novel or hear it in a theater play, students will probably never hear "for" used this way in a normal conversation. However, it can be useful to know, even if they don't have an opportunity to use it themselves.

Practice Makes Perfect

Once your students understand the unique points of both words, give them a chance to practice by conducting a short interview during the lesson.

Ask them questions like how long they've been studying English, how long they've been doing their favorite hobby, how long they plan to study overseas, etc., and ask them to answer in both "for" and "since" sentences (if appropriate). 

You can also quiz them by giving them a "since" statement and asking them to rephrase it as a "for" statement.

Exercises like these will help to establish the different usages in their minds, preparing them to use these important words skillfully in real-life situations. 

For more on explaining the differences between similar terms, check out the articles focusing on "Say"/"Tell" and "Look"/"See"/"Watch".

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