Lunch is a compound sign of eat/food and (mid)day, just as breakfast is the compound sign for eat/food and morning.
Teach your baby how to sign lunch when it's around time for this midday meal.
As your baby advances, it's good to have him or her aware of the time of day when certain foods are served. This sense of time will give your baby an added sense of freedom and agency to let you know when he or she is hungry and expecting to have a meal.
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