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The 15 Most Powerful Words in Subject Lines

Campaign Monitor - Feb 5, 2019

Article first published June 2014. Updated February 2019.

The inbox can be a hostile place. With a million other emails jostling for your subscribers’ limited attention, it’s important that you make your subject line stand out – and get your email opened. So, what works best?

We pored through thousands of campaigns to shortlist 15 popular words – and find out what makes an effective subject line.

While we’d love to say that we’ve found the “silver bullet” to getting people to open your email, our research indicates that, so far, there is no magical formula or golden combination of words that can guarantee an open. Sorry, everyone. What works best for a particular piece of content in one industry, does not ensure the same responses with another.

But, if you look at the data, there are certain patterns that emerge. So we can certainly provide pointers on how certain words perform, as well as practical tips for writing subject lines.

Finding our “Power Words”

In our initial study on subject line performance, we decided to look at how specific words influenced the open rates of campaigns overall.

We realized that in order to really understand the performance of certain words, we needed both a control group and a test group for comparison, being campaigns with words we had narrowed down for analysis.

Both the control and our test group made use of the same lists (minimum of 500 subscribers) between January 1, 2013 until March 31, 2014. In order to have enough data to be significant, the list had to receive at least 10 campaigns over that period.

This resulted in a sample of 3,941,735,015 recipients, from 360,872 campaigns and 11,207 lists.

From this modest sample, we narrowed down the most frequently used words that featured at the beginning and end of subject lines, then compared the open rates between our two groups to determine which words performed better, that is, which words increased the chance of an email being opened.

It’s cheesy, but we’ll call these high-performers our Power Words.

So, what makes a Power Word?

First, some quick notes about our word shortlist.

While some words boosted a subject line’s success when they featured as either the first or last word (eg. “Invitation”, or dates), others only provided a notable open % uplift at one end or the other of a subject line.

This is in part due to grammatical correctness: For example, a pronoun like “We” or present participle like “Introducing” would seldom feature at the end of a sentence.

Personally, I think it’s important to make these distinctions if only to highlight that word order and, more importantly, context matters.

As much as it would be lovely to string words together and see your open rates go up exponentially, there are no shortcuts to the ideal subject line.

We’ll share with you some of our other observations and advice, but let’s get into Power Words already:

So now that you’ve seen how Power Words can increase your open rate, let’s dig into the context that makes these words effective.

How can I improve my subject lines?

Power Words reveal a few lessons about how to rock your email subject lines. Keeping the above list in mind, we’ve highlighted a few key points that will help you achieve compelling subject lines that get the clicks you want.  

Catch your subscriber’s attention with more precise personalization

It’s said that a person’s favorite word is their own name, and the open rate above backs this up. Without a doubt, subject lines that are personally addressed to the recipient fare better than more generic greetings.

Using personalization tags in the email header is a great way to capture attention. See how it stands out?

Source: Biz Journals.

However, personalization extends beyond using a person’s name. You won’t fool anyone into thinking you care about them by including a short code that drops their name into the subject line and calling it done. Your recipients are smarter, seasoned in all the ways that marketers try to get their attention.

Instead, set yourself apart from the other emails in their inbox by taking advantage of data collection to create more bespoke subject lines. Doing so signals relevance and gives your recipient more of a reason to click on your email.

You can use things like:

• Birthdays and anniversaries
• Recent interactions with your site or brand
• Location
• Interests
• Information provided via surveys and feedback

To get the full scoop of how powerful personalization can really be, check out our guide on email personalization.

Leverage pronouns to deepen relationships

Don’t have your subscribers’ names handy? The popularity of “We” and “You/Your” shows that subject lines which address the reader are more likely to get a response if you’re using them well.

On one hand, pronouns are a short cut to personalization. According to linguists, they indicate relationships. Pronouns signal recognition between the individuals involved in the exchange.

For example, consider the fact that we’ve used the second person (you) to address you throughout this article. The pronoun helps us adopt a more conversational tone. Imagine if we’d chosen to avoid mentioning you at all. This post would sound a lot like we were talking to a wall rather than a person or it would read like an essay. Who wants to read that? 

In emails, pronouns operate the same way and you can leverage this feature in your subject line.

On the other hand, customers will recognize when you’re trying to create an artificial rapport with them. This occurs when customers don’t feel that a relationship exists with the brand in the first place. In such cases, the use of “we” to refer to the company and customer together arouses suspicion. It makes people wary of what you’re really up to.

Choose your pronouns carefully to elicit reactions, deepen relationships, and, yes, increase your email marketing open rates.

Inspire a sense of urgency and excitement

Urgency inspires action. So it’s no surprise that many of the Power Words on our list are either time-sensitive or evoke exclusiveness.

Holding your subscribers to a deadline to act or letting them know that they’re specially invited to partake can be a very persuasive tactic. Some psychological forces come to play here such as our innate hierarchy of needs.

Every Power Word on the list above plays to one of these needs. Likewise, these Power Words tell us that certain situations create excitement and urgency:

• The fear of missing out on a scarce item
• Deadlines to sign up, register for or buy something
• A sense that something is not well-known or available to the general public
• The opportunity to save money
• A solution to a problem
• The impression that something is new, innovative, and unique

A sense of urgency relies on creating meaning, demand, and value. What are you doing for your reader, and how might it affect them if they miss out?

Wrap up

These 15 Power Words to use in your email subject lines reveal a lot more than you’d think: They show how readers perceive and interact with the emails we send them.

In short, readers are more likely to engage with your email if they feel like you are speaking directly to them. Addressing people by name is an excellent tactic. Taking extra steps to personalize your subject line helps readers spot your email in a list of senders vying for their attention.

Leveraging words which promote and deepen relationships also promotes engagement when done right. Finally, indicating value and meaning helps create demand and excitement. Power words which elicit urgency take advantage of psychology to incite action.

Keeping in mind that the percentage changes noted above can be quite minimal in the grand scheme of things, it’s worth looking at subject line optimization within the bigger picture of open rate-maximizing tactics, including ensuring you keep a clean, engaged list and well, get into the inbox in the first place.