While your 18-month-old is as snuggly as ever, he's also changing. He's funny, has likes and dislikes -- and shows a clear personality. Your 18-month-old is learning new things and mastering new skills every day. Making sure he's developmentally on track gives you one less concern so you can focus on keeping up with him.
Having an 18-month-old in the house should warrant no small amount of childproofing. He's likely often on the move, walking and even running, although he's likely to run stiffly, falling easily or looking uncoordinated. According to MedlinePlus, an 18-month-old should have the coordination to build a tower using two or more blocks and to hold a cup and utensils to feed himself -- albeit messily. He should be able to at least partially undress himself and be able to pull a toy behind him and kick a ball. Many of his movements might seem clumsy, but should steadily improve over time.
Your 18-month-old's speech might still be mostly babbles, but you should be able to detect some real words within that gibberish. According to KidsHealth.org, a child this age will generally be able to speak between 10 and 20 words. He should be able to understand and follow basic commands. He might not obey every time you say "Stop hitting your sister!" but he should respond appropriately to instructions like "Come here," "Walk to your room" and "Pick up the ball" when accompanied by your gestures. Your child should also be able to communicate through his own gestures and pointing. He might run to a cabinet and reach up when he wants a snack inside, or be able to point to a certain body part when it hurts.
At 18 months, your child can accomplish more than he could at 6-months-old, but he might be even more attached to you than he was earlier. An 18-month-old will typically be extremely attached to his primary caregiver or caregivers, and he'll likely become upset when he's separated from you. He's also likely to show affection to others he knows well, according to the Centers for Disease Control and Prevention, but might seem nervous or shy when strangers come near. A child this age should be somewhat interested in other children, although he'll probably be protective of his own toys. He might try to imitate the things older siblings or other children do, although he's not likely to engage in much play with another child -- and might instead prefer to play by himself.
If your 18-month-old frequently tests your patience, he's probably developmentally on track. A child this age is generally strong-willed enough to throw tantrums when he doesn't get his way or when he doesn't get the attention he wants. Though he's likely still in diapers at this point, at 18 months, he might be show an interest in the toilet, and according to KidsHealth, you might notice his diapers are staying dry for longer periods of time. He might want to watch other people use the bathroom or try to copy an older sibling by sitting on a potty seat. He should sleep somewhere around 13 to 14 hours in a 24-hour period. He might also be ready to give up a morning nap, but that can vary. You can try giving him just an afternoon nap -- and see if that works for him.