Context usually makes it clear whether you are referring to the century or the decade. If confusion is possible, prefer to clarify: “the 20th century,” instead of “the 1900s.” Use of apostrophe An apostrophe before the s in the name of a century is unnecessary (though not incorrect) and generally omitted in formal writing. Examples

Other Question and Answers that can be helpful for you

1. What to write in a 20th century essay?

20th Century Essay 1 The Invention Of The 20th Century. 2 19th and 20th Century of Europe. 3 Technology During The 20th Century. 4 Gender Roles In 20th Century Advertising. 5 My Point Of View 20th Century. 6 Depiction Of Iran During The 20th Century.

2. How do you write out a century in writing?

Centuries may be written in either words or numerals. Note however that in formal writing, single-digit centuries (e.g., the ninth century) are generally spelled out instead of being written in figures. Double-digit centuries may be written either way (e.g., the 21st or the twenty-first century).

3. How do you write decades in an essay?

Generally, we recommend using numerals for decades. Use the entire four-digit number, place an ‘s’ at the end, and don’t use an apostrophe: The 1970s were the decade of disco, flared trousers, and moustaches. The most popular sitcom of the 1990s was Friends. Whatever style you choose for decades, make sure it’s consistent throughout your paper.

4. What was the world like in the twentieth century?

The twentieth century had been tumultuous, particularly during the former half, the world witnessing two major world wars, many revolutions and nationalist struggles, each holding a significant bearing on the other.