Final answer:
The predominant flavor in gin comes from the 'juniper berry,' Juniperus communis, which is actually a seed cone with a berry-like appearance. Juniper is essential for giving gin its characteristic piney and resinous flavor.
Step-by-step explanation:
The "berry" that gives gin its predominant flavor is not actually a berry at all, but rather a seed. This seed is none other than the juniper berry, scientifically known as Juniperus communis. While commonly referred to as berries, these are actually female seed cones with unusually fleshy and merged scales, which give them a berry-like appearance. Juniper is the crucial botanical that imparts gin with its distinctive piney and resinous flavor profile, which is central to the character of classic gin varieties.