It appears to be part of a plant, that is usually called a leaf.

You could say where you are, what it was attached to, even have a photo of the tree/shrub/vine/whatever it was attached to. Otherwise, it's a horrid guessing game.

Sorry, I'm new at this.
Here's a photo of the plant. It's in my veg garden but I don't remember planting it. I'm in southern Alberta, Canada.
Thanks

I thought it might be Lovage but the leaf doesn't look like photos I can find online.

Ambrosia for sure (ragweed)....species I'm not sure..but *I* have it too (lol), so I'll track it down.

Ambrosia trifida/Great Ragweed (just great...I hate it)

Crikey
Thanks

Is it safe to compost if it hasn't gone to seed?

Lovage leaves look and smell like celery, so they're pretty easy to spot (or smell).

Thanks. My more experienced neighbour told me it definitely wasn't a weed. I'll blame it on him, ha.

Yes, safe to compost. It is an annual plant so just chop it down and compost it. No need to dig it out or use herbicide.