To sign fat, form both hands into bent, open number 5 hands - or claws - then bring them together under your face and pull them apart. You can blow up your face to add emphasis to the pudginess while signing fat.
Teach your baby or toddler the fat sign when describing animals, people, cartoon characters, and so on. It is important though to underscore that this modifier -- like any of the other describing words -- is not meant as an insult. Teach it rather as an objective term of observation.
Teach your toddler this sign in conjunction with other personal modifiers pertaining to not just size or shape but height, age, and coloring as well.
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