Most Importantly or Most Important? Understanding the Difference

When you choose between “most important” and “most importantly,” you’re actually making a subtle grammar decision. It isn’t just a matter of preference. It affects clarity. It affects tone. And yes—it does matter in everyday writing and speaking.

Picture this: you say, “Most importantly, we need to arrive on time.” Another person writes, “The most important thing is that we arrive on time.” Both get across that arriving on time matters a lot—but they do it in different ways. And if you’re writing a blog post, an email, or a report, you’ll want to pick the one that fits best.

In this post you’ll learn:

• What “most important” and “most importantly” actually mean
• The grammar behind adjective vs. adverb and how that plays out here
• When to use each phrase (with real-life examples)
• Common mistakes and how to avoid them
• How these phrases behave in formal writing vs. casual usage
• Memory tricks so you’ll remember the difference next time
• Similar grammar confusions to keep an eye on
• Usage trends and how people are really using them today

By the end you’ll feel confident choosing “most important” or “most importantly”—and using them the way they were meant to be used. No more second-guessing. Let’s dive in.

Understanding the Grammar Behind “Most Important” and “Most Importantly”

Before picking sides, let’s unpack what each phrase actually does. The key difference lies in part of speech: adjective vs. adverb.

Here’s how grammar experts describe it:

• According to the Merriam‑Webster usage note: “more important” is a sentence adjective; “more importantly” is a sentence adverb. 
• A detailed discussion on English Stack Exchange explained: “’Most important’ is an adjective … while ‘most importantly’ is an adverb.” 
• So when you use most important, you’re describing what is important (a thing, a reason, a concept). When you use most importantly, you’re emphasizing how or in what manner the main thing happens (or the main idea is delivered).

When to Use “Most Important”

Use most important when you’re describing a noun—something that is the main thing, the top item, the priority.

Common scenarios

• You list several things and then say the most important [thing]:
  “Of all the changes we made, the most important one was updating our process.”
• You introduce a noun right after:
  “Her most important goal is to inspire others.”
• You emphasise a noun with “the”:
  “The most important factor in success is consistency.”

Tip

If you can “insert a word like ‘thing’, ‘matter’, ‘factor’ after the phrase,” it’s probably most important.
E.g., “The most imporant thing is that you show respect.”

Example sentence

• “In this experiment, the most important variable was temperature.”
• “My most important client expects weekly updates.”
• “Among all qualities, kindness is the most important.”

When to Use “Most Importantly”

Use most importantly when you’re modifying an action, an entire statement, or describing how something happens.

Common scenarios

• You start a sentence and you want to emphasize what matters most:
  “Most importantly, we need to keep our customers informed.”
• You tie together multiple actions and highlight the biggest one:
  “We improved design, streamlined shipping, and most importantly, reduced errors.”
• You want to stress manner or priority without pointing to a noun:
  “He performed with skill, grace, and most importantly, confidence.”

Example sentences

• “She prepared the report, contacted stakeholders, and most importantly, met the deadline.”
• “We’ll look at pricing, user experience, and most importantly, customer satisfaction.”
• “Most importantly, I hope you feel proud of what you achieved.”

Note

Some style-guides historically frowned on most importantly at the start of a sentence—arguing “more important” was preferable. But usage has shifted.

Common Mistakes and Confusions

Because “most important” and “most importantly” sound so similar, people often use them interchangeably—even when one is more fitting than the other. Here’s a look at typical mis-uses and how to fix them.

🚫 Mistake vs ✅ Correct

Why confusion happens

• Both phrases express emphasis—and so they sound almost interchangeable.
• Historical grammar advice sometimes said “more important” is right and “more importantly” wrong. But usage changed.
• In casual speech, many native speakers favor most importantly simply because it sounds natural—even when grammarians might argue for most important. 

Formal vs informal

In formal writing, leaning toward precision helps: pick the one that aligns with grammar rules (noun vs action). In casual writing, the choice is more flexible—but clarity should still come first.

Read More:“Spilled” vs. “Spilt” – What’s the Difference?

Real-Life Examples in Sentences

Let’s break down how both phrases appear in different contexts—so you can see them in the wild and choose the right one.

Everyday conversation

• “We cleaned the house, cooked dinner, and most importantly, spent time together.”
• “The most important thing is that you stayed safe.”

Academic writing

• “Among variables, the most important was socioeconomic status.”
• “Most importantly, the data show a clear trend toward rising temperatures.”

Business emails

• “We’re reviewing costs, adjusting deadlines, and most importantly, maintaining quality.”
• “The most important deliverable this quarter is the client presentation.”

Social media posts

• “I learned a lot this year. The most important lesson? Believe in yourself.”
• “Most importantly, thank you to everyone who supported me.”

Quotes

“Both more important and more importantly … are perfectly grammatical in sentences like ‘Most important/importantly, it’s logical.’” – Merriam-Webster usage note “The difference is that ‘most important’ is kind of like a noun, while ‘most importantly’ is an adverb.” – StackExchange answer 

“Most Important” vs. “Most Importantly” in Formal Writing

If you’re drafting a report, academic essay, or professional document, you might ask: which one is more accepted in this style? The short answer: both appear—but choosing the one that enhances clarity and tone is key.

What style guides say

• Some older guides insisted on most important when the clause implies “what is most important is …”
• Modern sources say both are standard and acceptable. Merriam-Webster observes: both have “steady use” in recent decades.
• In practice: watch your sentence structure—especially if you’re at the start of the sentence or modifying a noun vs action.

Practical advice for professional writing

• If you’re introducing a key point and modifying an action: start with Most importantly, …
• If you’re describing a keyconcept, noun, or priority: use the most important … or simply most important …
• Maintain consistency in tone. If you open with adverbial usage (most importantly…), keep that style. Don’t flip-flop in the same document.

Tricks to Remember the Difference

Let’s make this easy to recall. Try these memory aids:

• Adjective = most important → It describes a “thing.”
• Adverb = most importantly → It describes how something happens or modifies a whole statement.
• Mnemonic:
  Important = “the important thing”
  Importantly = “in an important way”
• Insert a quick test:
  If you can add the word thing (or matter) right after, use most important.
  E.g., “The most important thing is…”
  If you’re editing a verb, action or whole statement, use most importantly.
  E.g., “Most importantly, we must act now.”
• Short quiz (try yourself):
  1. “__ we finish by Friday, we’ll avoid penalties.” → Most importantly
  2. “The __ factor in his success was persistence.” → most important
  3. “She handled logistics, customer service and __, vendor relations.” → most importantly
  4. “Her __ goal is to promote wellness in the community.” → most important

Other Similar Grammar Confusions

Here are some other pairs of adjective/adverb that often confuse writers—and how the same logic applies:

The pattern: adjective describes a noun; adverb modifies the verb/statement. Same rule we see with “most important” vs “most importantly.”

Common Usage Trends (What People Actually Say)

Language evolves. What grammar books say and how people speak can drift. Here’s a look at current trends for our topic.

What the data shows

• Historically, more important (and by extension most important) had higher usage than more importantly.Recent decades show a rise in usage of more importantly / most importantly, making them very common and accepted. Grammar forums and usage notes suggest that resistance to most importantly is largely historical and less common now.

What this means for you

• If you hear most importantly in speech or read it in articles—yes, it’s totally in use and acceptable.
• But if you’re writing for a very formal audience (legal, academic, publishing house) you might lean toward most important when describing nouns to stay on the safe side.
• In blog posts, business writing, emails—use whichever fits the context and tone, just ensure clarity.

Final Thoughts: Which Should You Use?

Here’s a quick wrap-up to guide you next time:

• Use most important when you are describing the thing that matters most (noun usage).
• Use most importantly when you are describing how something happens, or introducing the key action or main point (adverb usage).
• Both are grammatically correct in many contexts—but your choice impacts clarity and tone.
• When in doubt, ask: Am I describing a noun or modifying an action/statement?
• People often overthink it—so focus on meaning and readability rather than getting hung up on “which is right.”

FAQ Section

Is “most importantly” grammatically correct?

Yes—modern usage guides accept it. It functions as a sentence adverb.

Can I start a sentence with “most important”?

Yes—but you generally need an implied phrase like “What is most important …” Example: Most important, the team stayed united.” That structure is acceptable though a bit formal.

Which is more formal?

There’s no hard rule. But many style-guides suggest “most important” for describing nouns in formal writing. “Most importantly” is fine too and widely used.

Are there differences between British and American English usage?

Usage patterns vary, but both varieties accept both phrases. Some British style-guides may lean more strictly toward “most important,” but the difference is minimal in modern practice.

What if I’m writing an academic paper or report

 Be consistent. Choose the form that best matches your sentence structure. If you’re describing factors or things: “most important.” If you’re leading with a statement or emphasising an action: “most importantly.” Check your institution’s style-guide if available.

Lily Grace