American actor Jennifer Aniston, who never shies away from speaking her mind, opened up about ageing, saying she doesn't "feel any different".

The actor, who turned 50 in February, spoke about how she felt entering a new decade of her life for the October cover story of InStyle, reported Us Weekly.

"Fifty was the first time I thought, 'Well, that number,'" Aniston said.

"I don't know what it is because I don't feel any different. Things aren't shutting down in any way," she added.

She also went on to say that she feels "physically incredible".

She added, "I feel physically incredible. So it's weird that it's all of a sudden getting telegraphed in a way that's like, 'You look amazing for your age.' I think we need to establish some etiquette around that dialogue and verbiage."

However, if there's one thing that Aniston doesn't like about ageing, is her grey hair.

"I'm not gonna lie -- I don't want grey hair," she said.

But nothing is going to slow her down. "Women were never allowed to have power. Power feels sexy to me today, as does women's intelligence and how capable and creative they are," she said of the current state of her career.

Aniston celebrated her birthday in February alongside family and friends, including ex-husband Brad Pitt at Sunset Tower in Los Angeles. Courtney Cox, Reese Witherspoon, George Clooney, and Amal Clooney, Jon Hamm, Kate Hudson, Lisa Kudrow, Robert Downey Jr, Laura Dern, were among some of the other pals who attended the grand birthday bash.

"Jen spoke to Brad briefly. At one point she hugged him and thanked him for coming," an insider told Us Weekly at that time, noting that other attendees "were surprised to see Brad there and were making a big deal of it".

"But it didn't seem like that big of a deal to Jen. The invite went out to a ton of people and he accepted. She was happy he was there, but that was it. She was busy making the rounds," the source added.

Another ex in attendance was singer John Mayer, whom Aniston dated on and off from February 2008 to March 2009. The two went through a widely publicised split but have stayed friends through the years.

Aniston's birthday came almost a year following her split from husband Justin Theroux but that didn't stop Theroux from wishing his former wife a happy birthday on social media.

"Happy Birthday to this fierce Woman. Fiercely loving. Fiercely kind. ....and fiercely funny," Theroux captioned the post.

Aniston kept the birthday celebrations going throughout February, even jetting off on a girls' trip with actor Courteney Cox. However, they suffered a minor mishap on their way to the tropical trip when their plane was forced to land after losing wheel mid-air.

On the work front, Aniston will be next seen in 'The Morning Show'.