Path.Combine(string, string)
Description

Concatenates two path strings.

If path1 does not end with a valid separator character DirectorySeparatorChar is appended to path1 prior to the concatenation.
//Remember to import IO to make Path work.
import System.IO;

function Start () { //This will print "FirstPathToSomeFileAt/foo.txt". Debug.Log(Path.Combine("FirstPath/To", "SomeFileAt/foo.txt")); }
using System.IO;
using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void Start() {
        Debug.Log(Path.Combine("FirstPath/To", "SomeFileAt/foo.txt"));
    }
}
import System.IO
import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def Start() as void:
		Debug.Log(Path.Combine('FirstPath/To', 'SomeFileAt/foo.txt'))