How Many Presidents Were Monoglots?
The first President of the United States came from humble beginnings with little formal education and only spoke English. Something that George Washington had in common with the 44th President (Barrack Obama) and 45th President (Donald Trump). However, many of the early Presidents spoke English, French and/or German. Others studied Ancient Greek and Latin in school and had a workable knowledge of second language. Although born in the United States, Martin Van Buren was raised in a Dutch community and was the only President that had to sequentially learn English as his second language.
President Trump, on the other hand, is the only monoglot in his immediate family. His current wife and First Lady Melania Trump is a polygot and speaks Slovenian, English, French, German and Serbian. Among his sons and daughters from different wives, each speaks more than one language. The President's granddaughter, Arabella, speaks Chinese Mandarin, something she shares in common with our 31st President, Herbert Hoover. Hoover attained a partial mastery of Chinese when he lived and worked in China during the late 1890s to shortly after the turn of the century.
Basic Categories of Lingualism
Yes, you're right. Lingualism is not a real word but you get the point. Although there is no definitive source, linguists agree that about half of the world's population is at least bilingual. Listed below are basic categories for speaking a language with a rough estimate by percentages:
Monolingual (speaking one language) - 40%
Bilingual (speaking two languages) - 43%
Trilingual (speaking three languages) - 13%
Multilingual (speaking four languages) - 3%
Polyglots* (speaking five or more languages) - 1%
An exact number of monoglots around the world is certainly a hard number to determine. That's due in part to the fact that some experts expect bilinguals to be perfect in two languages while others consider the ability to communicate in both languages as sufficient evidence. For now, the number of United States Presidents who spoke multiple languages is likely to mimic the percentages that are guess-timated for the world's population... roughly about one-half. To this day, the only polygot to hold the highest political office was Thomas Jefferson.
*NOTE: Some linguists consider someone who speaks four or more languages to be a polyglot. Linguistic study of multilingualism often adds simultaneous and sequential to classifications to denote whether multiple languages were learned at the same time as a native tongue.