As vs. because vs. since: When to use them

As vs. because vs. since: When to use them

by Andrea Byaruhanga

Updated November 21, 2022

As vs. because vs. since: They’re all part of a group of words called causal conjunctions. Their job is to introduce subordinate clauses and connect a reason to a result in a sentence. 

That means you can use them all the same way, right?

Well, kind of, but not exactly. 

Despite the fact that these words have similar jobs in sentences that are seemingly alike, they’re not identical. If you’re an English learner, you know that this can be the source of a lot of confusion. How do you know when to use “since,” “as” or “because” to ensure you have correct grammar?

Don’t worry—we’re going to clear a few things up for you. Let’s discuss the differences between these conjunctions and how to use each one. 

Learn languages at your pace

How to use “because”

The causal conjunction “because” is the most common and informal of the three conjunctions we’re discussing—and probably the least confusing too. Its typical form is because + subject + verb.

Here are some of its main features:

  • “Because” sentences are more focused on the reason rather than the result.

Example: “He was late for work today because there was a lot of traffic.” 

The purpose of the sentence is to provide a reason for his lateness.

  • “Because” is more common in the middle of a sentence than at the beginning

Example: A sentence like “I can’t come to the party because I’m sick” is a little more natural than “Because I’m sick, I can’t come to the party.”

  • However, “because” can be used at the beginning of a sentence (often in a slightly more formal context).

Example: “Because our fundraiser was such a success, we can now afford to 

renovate the school gymnasium.”  

  • You can use “because” to ask a question in which you’re suggesting an answer.

Example: “Are you going to take a vacation because you’re so stressed out?”

  • When you’re speaking or writing informally, you can start a sentence with “because” to answer a question. 

Example: Speaker 1: “Why do you look so sad today?” Speaker 2: “Because my best friend just moved to another country.”

  • You can use “because of” + noun/noun phrase to provide an explanation.

Example: I’ve been shopping much less often because of the price of groceries.”

Learn languages at your pace

How to use “as” and “since”

Although they’re not identical, “as” and “since” are used similarly, so we’re going to look at them together. These two conjunctions are both more formal than “because” and are slightly less strong when it comes to making a link between a reason and a result. Their form is as/since + subject + verb.

Here are a few more details:

  • “As” and “since” focus more on the result of a sentence rather than the reason. 

Example: “My daughter is unhappy at school as her teacher is unkind to her.” 

The purpose of the sentence is to highlight that your daughter is unhappy at school, which is the result of her teacher being unkind.

Example: “We’re looking for a house since we’ve outgrown our apartment.” 

The focus here is on trying to find a house—the result of having an apartment that’s too small.

  • Starting a sentence with a “since” or “as” clause is common. 

Example: “As I have an appointment this afternoon, I won’t be available to work.”

Example: “Since Christmas is next month, I need to start buying some gifts!”

  • “Since” is also an adverb indicating the passage of time from a specific point in the past until the present, so it can sometimes cause confusion in a sentence. 

Example: “He’s been in a good mood since he quit his job.” 

Here’s why that sentence is confusing: It’s unclear whether this means “He’s been in a good mood from the moment he quit his job up until the present time” or “He’s been in a good mood because he quit his job.” 

  • Similarly, “as” is an adverb that means “while”—this can also be confusing if your sentence isn’t clear.

Example: “She smiled as she was eating her favorite meal.” 

Does this mean that she smiled while she was eating her favorite meal, or because she was eating her favorite meal?

If you find that your sentence might be misinterpreted like the above examples, try rewording it so there’s no room for misunderstanding. 

As vs. because vs. since: Know the subtle differences

Although we’ve gone through the key features of these causal conjunctions, the truth is that the differences between them are sometimes not very obvious. To get a good grasp of this topic, review the information above, try putting it into practice whenever possible and, whenever you’re in doubt, using “because” is a pretty safe bet!

Learn languages at your pace

Andrea is a Canadian freelance writer and editor specializing in English, e-learning, EdTech, and SaaS. She has a background as an ESL teacher in beautiful Vancouver, British Columbia.  In her free time, Andrea loves hanging out with her husband and children, creating recipes in the kitchen, and reading fiction. She also loves camping and jumping into lakes whenever possible. Learn more about Andrea on LinkedIn or check out her website.

Related articles