You know about Murphy's Law (whatever can go wrong, will). And the Law of Averages (everything evens out in the end). And Newton's Third Law of Motion (every action has an equal and opposite reaction).

Well, The Laws of Parenthood incorporate a little bit of each of the above. And then some.

To wit:

1.) If you have an early appointment, or if the children need to be at school early for a field trip or other event, someone will be up at least twice during the night -- which means you will be, too.

2.) The toddler will sneeze mightily in your face the day before he comes down with a ferocious cold.

3.) Your kids' school or daycare will shut down due to Swine Flu the week after your kids have been out sick with a cold. (Corollary: Your kids will not have the H1N1/Swine Flu virus.)

4.) If you put something somewhere "for safekeeping," you will not be able to find it, but will remember having moved it from it's original location, which is the only place in which you can think to look for it.

5.) If you are the working mom of an infant, you will discover a cascade of dried spit-up on the back of your jacket, but only after you've worn it for at least two hours (or to at least one meeting). If you are the working dad of an infant, you will probably escape the spit-up baptismal, but will show up at work with a burp cloth tucked into your jacket.

6.) Any electronic device that's absolutely necessary to your sanity will be a.) missing or b.) out of batteries when you most need it.

7.) If you carry a purse, you will always have some sort of kid-type food in it, which you will discover when you are looking for something, like your ID. What you will not have in it is whatever you were actually looking for, like your ID.

8.) You will slave over an amazing meal that the kids won't touch, and you will throw together a last-minute "gotta get them fed" meal that they devour.

9.) You will not be able to find the signed permission slip you need to turn in to your child's teacher until after you have given up looking for it.

10.) You will go through the day with a sticky, kid-applied kiss on your cheek -- and, if you're lucky, you won't have to wash it off.

Which laws of parenthood apply to your life? Please share them -- I'm sure we can all relate!

Lylah M. Alphonse is a Globe staff member and mom and stepmom to five kids. She writes about juggling career and parenthood at The 36-Hour Day and blogs at Write. Edit. Repeat. E-mail her at lalphonse@globe.com.