“Decade”, “Century”, “Millennium”… – Here’s What Comes Next

We can give names to certain lengths of time when we write about them to make things easier. Most people already know about decades, centuries, and millenniums, but did you know more words can be used? This article will help you understand them.

What Comes After “Decade,” “Century,” And “Millennium”?

“Decade” is ten years, “century” is one hundred, and “millennium” is one thousand. After that, we can use words like Epoch for one million years and “Aeon” for one billion years. There aren’t many official words for other year types like 10,000 years, but we do have some unofficial variations.

Typically, official counting after millenniums is not possible. Nevertheless, we have some great words that work well with increasing values:

Decade	Ten years
Century	One hundred years
Millennium	One thousand years
Decem millennium	Ten thousand years
Centum millennium	One-hundred thousand years
Mega-annum or Epoch	One million years
Aeon	One billion years

How Many Years Is A “Decade”?

A decade is ten years in length. It’s one of the most common ways to reference ten-year periods, and we can use it to show that a certain amount of time has passed.

The definition of “decade,” according to The Cambridge Dictionary, is “a period of ten years, especially a period such as 2010 to 2019.”

You might be familiar with common phrases like “the 90s decade” or “the 00s decade.” These all work well to show that a period of ten years has taken place.

• It’s been a decade since we last saw each other.
• I was a kid in the 70s decade, and I loved every second of it.
• This decade is a joke! We need to move on to the next one!

How Many Years Is A “Century”?

A century is one hundred years. We use it whenever one hundred years have passed (i.e. from 2000 to 2100). It’s common to use this in history books to reference certain times when wars took place.

The definition of “century,” according to The Cambridge Dictionary, is “a period of 100 years.”

In most cases, we say the century that’s one above what you might expect. Since the years started at 0, the years 0-100 were known as the 1st century. Similarly, the current year is part of the 21st century (even though it’s only 2022).

• The 21st century has been a nightmare.
• I wish I was around in the 17th century.
• This isn’t the 18th century anymore. We have more power now!

How Many Years Is A “Millennium”?

A millennium is one thousand years. We are technically in the third millennium in time, but it’s rare for time to be spoken about in this way.

The definition of “millennium,” according to The Cambridge Dictionary, is “a period of 1,000 years, or the time when a period of 1,000 years ends.”

Millennium is much less common than a decade or century, but we still have a specific meaning associated with it.

• It’s been an interesting millennium, and the history books definitely show that!
• This millennium is going to be the most innovative one yet!

What Is A Period Of 10,000 Years Called?

If you follow the same Latin words are trends, then 10,000 years would be called the Decem millennium. While this is not the official name, it makes sense to refer to it in this way since we use Latin words to demonstrate every other type of year.

What Is A Period Of 100,000 Years Called?

Likewise, we can use Latin phrases to come up with the Centum millennium for 100,000 years. Again, it’s uncommon to see it used in any way since most people would rather use “one hundred thousand years” over the Latin form.

What Is A Period Of 1,000,000,000 Years Called?

One billion years is called an Aeon. It’s a well-known phrase that is used in certain scientific books or fantasy novels and games. While it’s not common to talk about one billion years in most contexts, we can attribute “Aeon” to the amount of time if needed.

What Are 20 Years Called?

A period of 20 years is known as a vicennial. However, this is not a common phrase, and many native speakers don’t know about it. Instead, most people simply use “two decades” to refer to a period of twenty years.

What Is Every 30 Years Called?

“Tricennial” is the correct term for 30 years. Again, this is not common, and many native speakers don’t know about the Latin form. Instead, they would simply use “three decades” if they wanted to talk about this period of time.

What Is A Period Of 50 Years Called?

You might be noticing a pattern here, and 50 years tend to follow the same idea.

Technically, 50 years is known as a semi-centennial. This refers to fifty years of time but is a Latin form that many native speakers don’t know about. Instead, they would either say “five decades” or “half a century.”

What Do You Call 100 Years?

100 years is a simple one. We use “century” to refer to it. Since it doesn’t use Latin forms in obvious ways, native speakers are familiar and comfortable with this form.

You’ll often hear people using “century” whenever they’re talking about 100 years. It’s best to remember it whenever you need to use it.

Is There A Word For 1 Million Years?

There is also a word for 1 million years that we haven’t touched on yet.

You can call 1 million years an Epoch or a mega-annum. “Mega-annum” works best if you want to stay true to the Latin form that includes the “mega-” prefix and “annum” (meaning year). “Epoch” is better if you’re using it scientifically or in a fantasy novel set.

What Is A Half Decade Called?

Finally, a half-decade is known as a quinquennial.

You might think this sounds a bit strange, and that opinion is shared by most native speakers. Therefore, it’s not a common form, and most people stick to the more simple term of “five years” or “half decade.”