Neda S. answered 05/15/19
PhD in Teaching English as a Second Language, Farsi native speaker
"yeki az" یکی از followed by a superlative means "one of the"
e.g: "yeki az behreteen ketabha" یکی از بهترین کتاب ها = one of the best books
"yeki az arzaantareen ghazaha" = یکی از ارزانترین غذاها one of the cheapest foods.
Also followed by a plural noun or pronoun
"yeki az inha" یکی از اینها = one of these
"yeki az dokhtarha" یکی از دخترها = one of the girls
in comparative form only "az" از is used and it will mean "than"
e.g: "Mina az Sara bolandtar ast" مینا از سارا بلندتر است Mina is taller than Sarah.
"chai az nooshaabe behtar ast" چای از نوشابه بهتر است Tea is better than Soda.
"Or" in Farsi equals "yaa" یا
e.g: "chai ya ghahveh?" چای یا قهوه؟ = tea or coffee?
"yaa" یا can also mean "either ... or "
e.g: "ya chai ya ghahve minoosham" یا چای یا قهوه می نوشم I (will) drink either tea or coffee.