A parliamentary system differs from a presidential system in government structure primarily through the relationship between the executive and legislative branches. In a parliamentary system, the executive (the Prime Minister) is derived from the legislative body and is accountable to it, allowing for greater collaboration between the two. Conversely, a presidential system features a separately elected executive who possesses distinct powers from the legislature, often resulting in checks and balances that can lead to political gridlock. These differences impact how policies are formed and implemented within each system.