NEW YORK (AFP) - Adele, whose separation ballad Someone Like You was an international blockbuster, has announced that her next album will be entitled 25 and will examine life on the cusp of adulthood.

Revealing details of the long-awaited follow-up, the English singer said that her 25th birthday marked a turning point.

"My last record was a break-up record and if I had to label this one, I would call it a make-up record," she wrote in a letter to fans posted on her social media accounts on Wednesday.

"I'm making up with myself. Making up for lost time. Making up for everything I ever did and never did," she wrote.

Adele - who is now 27 - said that turning 25 was "about getting to know who I've become without realising."

"Teetering on the edge of being an old adolescent and a fully-fledged adult, I made the decision to go into becoming who I'm going to be forever without a removal van full of my old junk," Adele wrote.

Referring to the wait since her last album in 2011, she wrote: "I'm sorry it took so long, but you know, life happened."

Adele did not reveal a release date for 25, amid industry speculation she will put it out in time for holiday shoppers at the end of the year.

Expectations of an imminent release rose on Sunday when a short advertisement during the British talent show The X Factor featured a blank screen with Adele's recognisable voice, singing a snippet to piano chords.

25 will be Adele's third album and follow a pattern as her previous works were entitled 19 and 21 - also after her ages.

21 - which featured Someone Like You and other hits including Rolling In The Deep - won the Grammy for Album of the Year and spent two consecutive years as the top-selling album in the United States.

In Britain, 21 is by far the best-selling album so far in the 21st century.

After the massive success, Adele said that she wanted a hiatus to give some time to herself.

While Someone Like You reflected on a breakup before her stardom, Adele in 2012 gave birth to a son with a new partner.