A presidential system is a system of government where an executive branch is led by a president who serves as both head of state and head of government. In such a system, this branch exists separately from the legislature, to which it is not responsible and which it cannot, in normal circumstances, dismiss.

The title president has been carried over from a time when such person actually presided over (sat in front of) the government body, as with the US President of the Continental Congress, before the executive function was split into a separate branch of government. After this split, the President was no longer needed to sit in front of the legislative body, although the executive title remained in legacy.

Although not exclusive to republics, and applied in the case of semi-constitutional monarchies where a monarch exercises power (both as head of state and chief of the executive branch of government) alongside a legislature, the term is often associated with republican systems in the Americas. Presidential systems are numerous and diverse, but the following are generally true of most such governments:

Shashi Tharoor (Malayalam: ശശി തരൂര്‍) (born 9 March 1956) is an Indian politician and a Member of Parliament (MP) from the Thiruvananthapuram constituency in Kerala. He previously served as the United Nations Under-Secretary General for Communications and Public Information^{[citation needed]} and as the Minister of State for the Ministry of External Affairs.

He is also an author and columnist.

Shashi Tharoor was born in London to Lily and Chandran Tharoor, both Malayalis, hailing from the state of Kerala^{[citation needed]}. Tharoor studied at Montfort School in Yercaud and Campion School in Mumbai^{[citation needed]}. He attended high school at St. Xavier’s Collegiate School in Kolkata and obtained his Bachelor of Arts degree in history from St. Stephen’s College, Delhi.

He went on to win a scholarship to study at The Fletcher School of Law and Diplomacy at Tufts University and earned three degrees in three years - a Ph.D. and two master's degrees at the age of 22, Tharoor is the youngest person in the history of the Fletcher School to be awarded a doctorate. His doctoral thesis, "Reasons of State", was a required reading in courses on Indian foreign-policy making. In 2000, Tharoor was awarded an honorary Doctor of Letters degree^{[citation needed]} by the University of Puget Sound and in 2008 he received an honorary doctorate degree by the University of Bucharest^{[citation needed]}.

Israr Ahmad (December 19, 1940 – April 2, 2010) was an Indian theoretical nuclear physicist and professor at Aligarh Muslim University since 1961. He was known for his work in quantum scattering theory.

He was an associate member of the International Center for Theoretical Physics located in Trieste (Italy), a member of the New York Academy of Sciences, and the Indian Physics Association. He was Founding Director of the Center for Promotion of Science at the Aligarh Muslim University from its inception in 1985 to 1991, and Chairman of its Department of Physics from 1988 to 1991. He was editor of the monthly Urdu journal Tahzibul Akhlaq of Aligarh Muslim University from June 1986 to 1990. In addition, he had served as professor at King Abdul Aziz University in Saudi Arabia. He was married to Mahe Laka (daughter of Dr. Qammrudeen).

Apart from his scientific work, Ahmad was keen in spreading the message of Islamic reformer Sir Syed Ahmad Khan. He was one of the strong supporters of the Aligarh Movement and revived the mission of Sir Syed to promote modern education, especially science, among oriental students and seminaries. To achieve this, with the support of Dr. Abdus Salam, he established the Centre for Promotion of Science (CPS) at AMU Aligarh in 1985, and was appointed as Founder Director of the center.

Eric Eustace Williams (25 September 1911 – 29 March 1981) served as the first Prime Minister of Trinidad and Tobago. He served from 1956 until his death in 1981. He was also a noted Caribbean historian, and is widely regarded as "The Father of The Nation."

Williams' father was a minor civil servant, and his mother was a descendant of the French Creole elite. Eric Williams was a descendant of the de Boissiere family which is known for its public service, charity, and focus on human rights. He was educated at Queen's Royal College in Port of Spain, where he excelled at academics and football. He won an island scholarship in 1932 which allowed him to attend St Catherine's Society, Oxford (which subsequently became St Catherine's College, Oxford). In 1935, he received first class honours for his B.A in history, and was ranked in first place among University of Oxford students graduating in History in 1935. He also represented the university in soccer. In 1938 he went on to obtain his doctorate (see section below). In Inward Hunger, his autobiography, he described his experience of racism in Great Britain, and the impact on him of his travels in Germany after the Nazi seizure of power.