What’s the Difference Between Optimum and Optimal?

Optimum versus optimal: Are they interchangeable?

I say no, but not everyone agrees.

I discussed the difference in a February 15, 2015, post that followed the Super Bowl that year. Because I always ask new blog subscribers how they found me, and because I continue to get mentions of that optimum versus optimal post, I’m covering the topic again.

Here are two lines from the news article about the Super Bowl that prompted the original post:

Coach Pete Carroll’s call for a pass was as far from optimum as Seahawks fans could imagine.

The strategy Coach Pete Carroll chose was not considered the optimal choice by many Seahawks fans.

History of optimum

According to merriam-webster.com, scientists in the mid-19th century needed a word to describe the most favorable point, degree or amount; the best condition for the growth and reproduction of an organism. They took “optimus” from Latin to create the noun optimum.

It filled the scientific need, and optimum eventually gained use beyond the scientific community to broadly imply the best or most desirable.

A few decades later, optimum was being used as an adjective as well as a noun. That’s when optimal was coined to serve as an adjective, but the distinction is either not understood or not accepted by everyone.

A popular resource for writers, Garner’s Modern American Usage, prefers “optimum” as the noun and “optimal” the adjective.

Noun Examples: optimum

These examples show how optimum is used as a noun (the best condition or amount):

Professor Albertson was pleased that the soil conditions of the test garden finally reached their optimum.

The pass interception yielded the optimum the coach could have hoped for.

Your thorough preparation resulted in the optimum your job search could have achieved.

Adjective examples: optimal

These examples show how optimal is used as an adjective (the most desirable, most favorable, most effective). Note that optimal is followed by the element it modifies:

Once students achieved optimal soil conditions for the test garden, the plants thrived.

The quarterback’s injury contributed to an optimal opportunity for a pass interception.

Because of your thorough preparation, your achieved optimal results from your job search.

I align with those who recognize and appreciate the distinction between optimum and optimal. Consider these pairs of words that follow the same noun / adjective pattern as do optimum and optimal:

 

bacterium / bacterial

cerebrum / cerebral

cranium / cranial

minimum / minimal

I ask again as I did two years ago: If optimum and optimal mean the same thing — if they are interchangeable — why do both words exist?

Choosing one word over another because of its precise meaning or nuance separates the thorough writer, editor or publication from the rest.

Please share this post with others who will benefit from learning the distinction.

 

Kathy Watson
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Kathy Watson

Kathy has a love/hate relationship with grammar; she loves words and the punctuation that helps them make sense, yet she hates those pesky rules. A self-proclaimed ruthless editor, she prefers standard usage guidelines of The Associated Press Stylebook. Her easy-to-use Grammar for People Who Hate Rules helps people write and speak with authority and confidence. She encourages and welcomes questions and comments. (Email)

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2 thoughts on “What’s the Difference Between Optimum and Optimal?

  1. Charles Myhill

    I agree with you, Kathy. As you say, ‘Choosing one word over another because of its precise meaning or nuance separates the thorough writer, editor or publication from the rest.’
    Warm regards
    Charles

    Reply

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