Bash

#!/bin/bash

function fibonacci {

	local n=$1

	[[ $n == 0 ]] && echo $n && return
	[[ $n == 1 ]] && echo $n && return

	local x=$(fibonacci $((n - 1)))
	local y=$(fibonacci $((n - 2)))

	echo $((x + y))
}

echo -e sh\\t$(fibonacci 14)

C

#include <stdio.h>

unsigned int fibonacci(const unsigned int);

int main()
{
	printf("c\t%d\n", fibonacci(14));

	return 0l;
}

unsigned int fibonacci(const unsigned int n)
{

	return (
		n < 2 ? n :
			fibonacci( n - 1ul ) + fibonacci( n - 2ul )
	);
}

Haskell

#!/usr/bin/runhaskell

fibonacci :: Int -> Int
fibonacci 0 = 0
fibonacci 1 = 1
fibonacci n = fibonacci (n - 1) + fibonacci (n - 2)

main = putStrLn ("hs\t" ++ show (fibonacci 14))

Lua

#!/usr/bin/lua5.3

function fibonacci(n)

	if n < 2 then return n end
	return fibonacci(n - 1) + fibonacci(n - 2)
end

print("lua", fibonacci(14))