
Pomegranate syrup is a sweet, thick red syrup made from pomegranate juice and sugar, used to sweeten, color, and add fruit character to drinks.
Color and sweetness with a tannic fruit underneath, and the tannin is the tell: made properly this is fruit and sugar, while many commercial bottles carry no pomegranate at all.
Grenadine
One product, two names. Which word a bottle carries tells you nothing about whether pomegranate is in it. If a recipe names one and the shelf holds the other, nothing needs adjusting.
Pomegranate molasses
Reduced without sugar into a sharply sour paste for cooking, and far more concentrated; a spoonful sours a drink instead of sweetening it.
Homemade keeps a fortnight refrigerated and darkens as it goes. A commercial bottle keeps for months on sugar and preservatives. Neither improves with time.