Being conditional upon simply means that something is subject to a particular condition or requirement. However, sometimes using the same phrase over and over can become monotonous. So, to spice things up a bit, one can use different terms to convey the same meaning. One such synonym for being conditional upon is contingent upon. This implies that something is dependent on a particular condition or event taking place. Another synonym that can be used is subject to. This phrase suggests that something is liable or susceptible to a particular condition. So, the next time you're writing something, try using these synonyms instead of repeatedly using the same phrase.