For me, one of the side effects of aging is an inability to understand song lyrics. Another is the inability to recognize that former teen singers, like, say Britney, are now adults. Singing adult songs. With very adult meanings.

So for the past few weeks, every time her latest single, “3,” came on the radio, I cranked it up. I mean, it’s a great car-dancing song. And the kids like the whole counting thing. I couldn’t really understand the lyrics, but  really — it seemed to be a lot of counting and harmless, meaningless rhyming.

Last night, I pulled up the video. And as I watched the dancing, things suddenly clicked into place.

Whoops, I thought, speedily Googling the lyrics and wondering what on earth my daughter might have been trilling on the school playground lately.

A quick read of the lyrics revealed that the princess of pop was indeed singing about threesomes. As in, two on one. As in, menage a trois.

I don’t know why I was so surprised. I’m the woman who was probably the last on the planet to realize that Lady Gaga’s “Pokerface” wasn’t actually about poker. Duh.

I’m not a prude. And both songs will remain on my playlist because — hello!  — they’re great workout and dance songs.

But Tootie — well, let’s just say that she’ll no longer be counting along with Britney.