Some signs that your 2-year old may be developmentally delayed would be if they're not walking, if they're not talking, if they're not able to understand simple phrases, if they don't understand who you are.
In other words, if they're not pointing to you when you're saying mommy. If they're not responding to you, if they're withdrawn, if they are not engaged. And what engagement means really is are they looking at you, is there that shared attention, can you look at them and see that their understanding what you're saying.
Or if you're talking to them are they staring at the ceiling? Or are they going off into the corner and completely withdrawn? Those are some areas for concern. Any time your child loses a skill that they once had, is another area for concern.
So that could be something like if they were talking to you, if they were able to say my cup please mommy or mommy my cup, and all of a sudden they're not saying that, that is cause for concern. And above all else, trust your instincts. You know as a parent your child better than anyone and if you feel for any reason that there may be a delay in your child's development, do not delay in seeking help or advice.
And by that, go speak with your child's pediatrician and have a discussion on your child's development.