What does 2 centimeters dilated and 40 percent effaced mean?

These are terms used during childbirth to indicate the progression of labor. Once you get to that point, the kid is on it's way and you probably should stay near the hospital. If you are having contraction pains the answer above is probably correct but many women walk around for days at this dilation so don't panic yjr dilation ahs to go to 10cm and effacement to 100% before you have the baby and it is contractions which do it.

Dilation refers to how far your cervix has actually opened.
Effacement refers to how much it has thinned out or pulled upwards. Don't put too much on the numbers - you can go from low numbers to high very quickly ( so don't be discouraged by staff who tell you 'you'll be hours yet'. They may be right but the discouragement itself can slow things up.). On the other hand, as mentioned above, it can be happening without you knowing much until your body has already done a lot of the work.