using System;
using System.Linq;
using System.IO;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		var s = "Match word but not word1, w1ord or word!";
		var res_linq = s.Split().Where(x => x.All(c => (c >= 65 && c <= 90) || c >=97 && c<= 122));
		Console.WriteLine(string.Join(";", res_linq));
		// REGEX
		var res_regex = Regex.Matches(s, @"(?<!\S)[a-zA-Z]+(?!\S)").Cast<Match>().Select(m=>m.Value);
        Console.WriteLine(string.Join(";", res_regex));
	}
}