He was the first to use the phrase ‘function
of x’ John Bernoulli (1667-1748) used the notation φx for the first time in 1718 to
indicate a function of x But the general adoption of symbols like f, F, φ, ψ to
represent functions was made by Leonhard Euler (1707-1783) in 1734 in the first
part of his manuscript “Analysis Infinitorium”